Your lathe is different in some design features, but nothing totally unusual. Tapered journals in bronze bushes were commonly used.
Here is how I'd approach the matter of setting up your headstock:
1. clean the bronze bushes with solvent and wipe with something like paper shop wipes. Inspect using a good light, looking for burrs or scoring (grooves or gouges). My test is to run my fingernail over anything that catches the light or catches my eye. Light can make things look a lot worse sometimes. I drag my index fingernal over machined surfaces such as bearings and journals. If a scratch or gouge or burr catches my fingernail, I consider it "too much".
2. Using a small scraper, take down any burrs or raised metal in the bronze bushes which might have caught your fingernail. Scrapers can be made from a piece of broken hacksaw blade (radius the corners so it does not dig or gouge the bronze), or a small three corner scraper or bearing scraper.
Using something like a small three-corner scraper (make from a piece of old triangualr saw file), put a very small chamfer on the corners of the bushing bore mouths. This "breaks the corners" and may clean off any burrs that developed during previous owner's adjustment or reassembly efforts. The three corner scraper will put a nice chamfer on if you use a drawing motion, kind of "slicing" or "shearing". When you use a three corner scraper correctly, it will not dig in, nor will it chatter. You want to make a tiny chamfer, not more than about 1/32" x 45 degrees. This breaks the corners and makes it less likely you will ding or push up the bronze during reassembly.
Get some "Scotchbrite" abrasive pads of the finest grit. Using something like penetrating oil or kerosene (I believe you might call it "parafin") amd the Scotchbrite pad, lightly polish the inside of the bronze bushings. Wash the bushings well using solvent (I use automotive brake parts cleaner) and paper shop wipers. Make sure the bearings are thoroughly cleaned inside and out.
3. Give the inside of the bushings the next test: lightly drag your fingertip (assuming is not heavily callused) over the bronze inside of the bushing. It should be smooth, nothing "catching" your fingertip.
4. Using a fine hard pocket oil stone (I use either an "India Medium Hard" or an "Arkansas Hard" depending on the condition of the parts), tone off the journals. All you are looking to do is break the surface glazing and take off any miniscule burrs or sharp edges to any ridging or scoring (result of wear). Use the oil stones in a criss-cross pattern and use something like kerosene or penetrating oil with the oil stones. Again, use the fingernail test on the journals to be sure there are no ridges or sharp-vee scoring. You are not looking to remove metal, just "kiss off" the surfaces of the journals.
5. Try assembling the spindle and rear journal. It should fit very snugly, but not need to be driven on with any real force. Make sure the shaft key for the rear journal is free from burrs as well. Do a trial assembly of the spindle and rear journal to be sure it goes together without having to beat on it.
The rear journal has to move on the spindle to set the sprindle bearing clearance and end play.
6. When you have everything cleaned up, reassemble the lathe headstock. My way of approaching this is to do the following:
1. check the pitch of the threads on the adjusting nuts. This is going to become your built in micrometer.
Measure the length and big and small end diameters of the journals. Do some trig and you will have the angle of the taper on the journals.
If you play with the tangent of the half-angle of the taper, you will get the relationship of axial move (adjuster nuts do this) to side wards move
(bearing side clearance).
2. Reassemble the headstock with just some penetrating oil or thin lubricant on the journals and bushings.
3. Run the adjuster nuts in until you cannot turn the spindle by hand. This is necessary to seat the bushings and to get yourself a starting point.
Do not hammer or put any real torque on the adjuster nuts. Just snug them until you can't turn the spindle. This takes out all the lash or
play.
4. Now we get to the "built in micrometer". If you have measured the pitch of the adjuster nut threads, you will know how far one full turn of the
adjuster nut advances or closes in. If you have done your trig, you also know how much an axial move of the adjuster nuts is going to change
the side clearance of the bearings. Use any available means to divide the circumference of the aduster nut (I'd use the spanner slots as
divisions and take portions of a "slot" as basis for figuring my moves).
5. Back off the adjuster nuts the amount you calculated and gently lock them snug.
6. Tap the ends of the spindle with a piece of hardwood and hammer. This will open up the clearance since the cone journals may well be seated
hard in the bushings.
7. Try turning the spindle. If it turns free, check side clearance using a dial indicator. To do this:
Mount a dial indicator so it is at 12:00 on the "register" or collar of the spindle. Zero the indicator.
Put a piece of hardwood such as a hammer handle in the bore of the spindle. Push down as hard as you can, estimating 50-75 lbs of force.
See how the indicator moves and re-zero it while pushing down on the hardwood handle.
Pull UP on the hardwood handle, again estimated 50-75 lbs of force. Note the indicator reading. This is your radial or side clearance in the
bearing. 9100 has a good value for typical side clearances. If you do not read at least 0.001" on the dial indicator, back off on the adjuster
nuts a very small amount. Again, your "built in micrometer" based on the thread pitch and angle of the journal cones is your guide. A nudge
of the adjuster nuts is usually sufficient.
8. Once you have the adjustment, you will need to lock it in. This means using two spanners. As crazy as this sounds, if you tighten the locking nut against the adjusting nut, you may actually change the amount of clearance in the bearing. Pulling the lash or any slight slop out of the threads is the reason. After you lock the adjuster nut, recheck the clearance and feel of the bearing to be sure.
9. Once you have the bearing clearances set, put some light oil (ISO 46 or perhaps a touch lighter) into the spindle bearings and roll the spindle by hand. Feel how it stops. It should glide to a stop. If it stops abruptly or with a noticeable "jerkiness" when you stop turning the headstock pulley, it is too tight.
10. If the spindle glides to a stop, you are ready for a heat run. Belt up the lathe and run at its lowest speed. Keep feeling the bearings for warmth. If the spindle seems to be getting hot in a hurry, stop the lathe immediately and flood the bearings with more oil. When the bearings cool, readjust and open the clearances slightly. You are going for a balance between enough clearance so the lathe spindle can run without overheating/seizing, vs tight enough clearance so the lathe can turn stock without the stock "climbing the toolbit".
11. My own judge of spindle bearing heat is crude. I use the back of my hand, like I'd feel another person's forehead for fever. If the spindle
bearing housings on the headstock are so hot you cannot keep a hand on them, they are too hot. 140 degrees F, if you have means to measure the temperature is the upper limit. A "nice warmth" is what you need to feel when the spindle has been turning for 5 minutes or more.
12. The heat run is done for 5-10 minutes at lowest speed (not in back gears, but "direct" belted). Once the spindle reaches temperature and seems to have stabilized, stop the lathe and move the belt to the next step of the cone pulleys to speed it up. Repeat the procedure for feeling and checking temperatures for each step of the cone pulleys until you have the lathe running at maximum spindle speed.
13. Once you have made your heat run, you can go to the next step. That is to chuck a piece of round stock, say 1" diameter, and take a cut on it. By not having the stock supported on the tailstock center, you get to check how rigidly the headstock bearings are supporting the spindle.
Points to remember:
-Bronze has a greater coefficient of thermal expansion than steel. Spindle clearances that seem loose when cold will "tighten up" or "close up" as the lathe is run. As the spindle and bearings warm, the clearances will get tighter. This is why a heat run is made very gradually when you have had a plain bearing headstock apart and made adjustments to the bearings.
-Plain bearings rely on "hydrodynamic lubrication", or the famous "wedge shaped film" of oil. When running, there ideally is no metal-to-metal contact between the journals and the bearing bushings. Too tight or too loose a clearance and the oil can;t establish and maintain this wedge.
-Oil for plain bearing spindles is a whole 'nother subject for splitting hairs, theorizing, debate and dischord. Old lathes and oldtime machinists did not have a whole plethora of lubricants available nor did ISO designations exist. The majot mistake a lot of people used to make was to run something like 30 weight auto engine oil in their lathe's spindle bearings. This is a bit too heavy. Things got worse once multi-viscosity and detergent automotive engine oils arrived. Avoid using them. I personally use nothing more than "Tractor Hydraulic Oil". This is typically a DTE Medium or DTE Heavy Medium oil. It is mineral based, straight weight, and has anti corrosion and anti foaming additives. Tractor hydraulic oil comes typically in ISO 46 & ISO 68 weights. Either will work. I've been running ISO 46 in the headstock bearings of my Southbend Heavy 10" lathe and Southbend Light 10" lathe for many years.
-Use your senses and your head, and go slowly with the work of putting the lathe back in service. A lot of what is needed to put the lathe back in service is simple, no reliance on fancy instruments (other than a dial indicator). No need to overcomplicate things.