I think I got my M-head manual from Ozark. We have several manuals for the J-head and newer BP's, which I think do well enough explaining basic construction, maintenance, and operation. Having some diagrams of the what's different with the M-head/round ram helps though.
Concerning the spindle bearings and their lubrication: on mine I believe the pulley bearings are sealed while the rest are all open face, so by my understanding the oil doesn't need to go up from the oil cup, just down. The spindle bearings of course need a pre-load and dictate the amount of precision in the head, but the pulley bearings don't see any axial load and don't require the same level of precision so sealed bearings should work fine.
When I started working on my 1941 M-head BP (came with our 2006 shop merger), I put a tool in the spindle and started cutting and noticed the finish was terrible and my cutter kept slipping down, then I realized the tool was fine, the spindle was falling out of the machine! I opened it up to find that the take-up nut on top of the bearings had come loose and messed up the threads. Luckily I had a Timken tapered nut on hand that matched the original perfectly (stock from another application) and I was able to chuck the spindle up and single point the thread back to usable shape. I wasn't sure how long it had been run with the loose nut but I took a gamble and put it back together with the existing bearings and made sure that the nut was secured with the sheet-metal locking tabs, and it's been working fine for a 5-6 years now. Finish is fine and no noticeable run-out. Granted I'm not jig-boring with it, but it works fine for 1/2HP .005-.001 tolerance work.
