I came up in the era where the old workhorses like that R & P, or the Hendeys or LeBlonds were in common use. High Speed Steel toolbits were also in common use, particularly for form tools. I never transitioned into the more modern shops, as I got my degree and went to work on powerplant construction, then as an erector, and then spent 32 years with the NY Power Authority. The result was my machine shop experience was often based on one-off jobs, repair jobs, and very heavy machine work associated with hydro turbines and generators. Having a lathe capable of higher spindle speeds was never in issue in the world I worked in. Having lathes with enough iron in them to stand up to the work we did was what counted, so we bought used LeBlond lathes rather than new imports.
Using high speed steel toolbits on an old lathe like the R & P, you can do a surprising amount of work and it will be good work. 'Ginning up the speed of an old lathe like an R & P geared head lathe is not something I'd do without some careful inspection of the headstock internals, particularly the lubrication system. As I said, the gearing in those R & P lathes is likely heavy spur gears, not meant for high speed running. Add a chuck that is also not statically balanced, and the makings of some heavy vibration are all there if the lathe is run at much more than maximum design speed.
In my world, we still deal with forgings and castings. In addition, we machine weldments, or worn parts built up with welding. I think nothing of building up a worn shaft or fabricating a part using "stick" welding (DC SMAW). I clean the welds with air grinder and wire wheel or run a needle scaler over them, then the parts go into the lathe. On the railroad, we used to take chunks of old freight car axles and make parts and tools out of them. We'd cut a chunk out of an old freight car axle with a torch, clean it up with a grinder and wire wheel, snag off the slag and put it into the R & P lathe. We eventually put a Phase II knockoff of an Aloris or Dorian toolpost on that R & P, as the lantern toolpost and regular tool holder would not stay in place on heavier cuts.
The apron on an R & P lathe has (if I recall correctly), an oil pump that is actuated when the carriage moves. I'd suggest flushing the apron with kerosene or diesel fuel to get rid of any old oil and sludge before putting the lathe into service. I'd do the same thing with the headstock. We never had a manual for our R & P lathe. I got a 5 gallon pail of Tractor Hydraulic Oil, which is an ISO 46 oil, classified also as a DTE Light oil. It is a straight weight mineral oil with additives for corrosion inhibiting and antifoaming. No detergents, no antiwear additives- this latter being bad news for some of the yellow metal bearings.
We run Tractor Hydraulic Oil in the old R & P as well as other similar geared head machine tools of that same era. We run way lube or bar-and-chain oil in the apron.
These lathes are like old draft horses. Made for slow heavy pulling, and at their age, a little loose and maybe a little swaybacked, but still have plenty of work left in them. The trick is learning to work with an old lathe. Bedway wear often looks worse than it actually is. If you take a lathe with a bed having ridges worn in the area near the headstock and turn a piece of stock stuck out of the chuck, you will be surprise at how little taper there actually is. Doing the trigonometry to calculate what the "drop" of the bedways does to the taper of the work will show it takes a lot more wear to produce anything too serious. As I said, these are old lathes, and at this point, an old R & P, unless it lived in a prototype shop or a similar type of environment, will have had 60+ years of use and its maintenance history as far as being kept cleaned and lubed is anyone's guess. I would not expect toolroom grade work from this kind of lathe, but I would take it as-is, and have no problem turning out work within a thousandth or two. Learning to work with the lathe, working with a cross feed which might have 0.050" or more backlash, and a worn set of bedways, you can do some fine work. Learning to work within the design envelope of these old lathes is the other piece of the puzzle. Do not expect to run indexable carbide tooling at the speeds and feeds modern lathes would run at. Using HSS toolbits and drills, you can remove plenty of metal plenty fast. And, with HSS toolbits, you can stone a radius on them and get a fine surface finish, or grind a form tool or threading tool without having to order special inserts or having a diamond grinder on hand. A bench grinder and oil stone are all you need to grind and stone HSS toolbits.
I'd look for anything obviously missing or broken off. Handlevers are often the victims of careless moving of the machine tools, or some other mishandling in the shops. ALl too often, I've seen old machine tools with "stumps" of broken off levers, with the fractures covered with years of grunge. People resort to vise grips and makeshifts on some of these situations. A compound rest ball crank goes missing, so a lathe dog winds up on the compound rest screw. These are makeshift repairs, and the lathes keep on being used. Or, the busted levers are brazed together and about twice as much braze metal as needed is laid on. Works fine, just doesn't look so good. More important is to be sure all the gearing is intact and working properly- in the headstock, quick change box and in the apron. R & P used a multiple plate clutch, and if you can try the lathe under power, make sure this engages and disengages properly. I've never had to adjust one of those clutches. Got lucky with old lathes, I guess.
I am sure, if you want a solid workhorse of a lathe capable of heavier work, the R & P will be fine. Stuff like turning a brake rotor, facing an auto engine flywheel, or machining built up repairs or boring an occasional compressor or engine cylinder are all the kinds of jobs the R & P will handle quite well.