Sad to say these machines were intended for ten to fifteen years of hard harsh work to be recycled as was considered in the Day. The engineers even as did not build them to be worked on built impressively long lasting mechanisms, reasonably cheap, well constructed and durable to the point I am still using a 45 year old machine.
Minnpar has parts manuals from Allis on these and are downloadable. Service and operations manuals still exist as reproductions, if buy one of the machines the necessity to buy the manuals is already there before ever drop bucket to earth.
I am steady in process on my old beater, rails should be off it in a month if I am lucky, then will have a set that with a pin/bushing turn should be good enough for personal use. Bought a set of six used links(still assembled) from Idaho(General Gear) for replacing the master links on these chains as the pin eyes are completely beaten open beyond further use. Having a machine shop turn or grind down the pins for master pins would also be in store as neither links nor pins and bushings really exist in any volume. Already e-mailed much of the initial nuances to see if even worth picking the machine up. Has to run, has to at least engage trans and brakes/clutches or is already a money pit with next to no bottom.