hello G_Dj
oh this one's an older one huh?
i do remember some of those older ones made that way with a brass bushing instead of ball bearings. Just don't see many these days :o)
But yeah you can use some degreaser and clean off the parts where the outer roller ring contacts the front and rear track, you can leave grease on the side unless it also has a roller for side thrust. Those older ones sometimes used brass plugs that were adjustable so you can remove most of the side freeplay out. Does it have these adjusters in the center of the stub shaft that the roller mounts on? The adjustable screw will be on the inside of the carriage where the stubshaft is mounted and is probably an allen head screw with a lock nut on it, it could be a regular bolt or a screwdriver straight slot screw or something like that.

To answer the question about washers between the roller and stub shaft weld? yes there would and usually are shim washers there to hold it out away from the inside weld and stub shaft mount plate. If the roller is rubbing the weld that might well be why they are not turning. There is a likely chance these spacer shim washers are specific to the size of the shaft and also sized so they will not be too big on the OD side and protrude out rubbing anything on the OD side. Would i be correct in an assumption that there are NOT any snap rings holding these rollers on? Sometimes there are, but on some older lifts they did not. If the stub shaft has a groove cut out near the end of the shaft being exposed after you install the bearing then i would say yes it has a retainer snap ring. Or if there are no brass plugs in the end of the stub shaft but you see a threaded hole? Then that could be the retaining method using a flat head bolt and washer to hold the bearing on. I never had many allis trucks in my route to work on but i have dealt with them a time or 2 in my career along with alot of other makes and models over the years so i've just threw out a bunch of several ways they may mount and possibly retained on the shafts.

If by chance the stub shafts do have adjusters with brass plugs you'll need to de-adjust them, then as you are installing the bearings you have to test fit the carriage in the mast and make sure you have clearance between the side of the bearings and the channel side from top to bottom and apply your shims according to the over all side thrust you see as it travels from top to bottom. You may notice it might get narrower towards the top than at the bottom because the bottom channel does tend to take more hits and can get expanded slightly from the impact force from hitting things while the forks are lowered. (just something to keep in mind while you are measuring OAW when setting the shims on the rollers).
Once you are finished it should travel freely from top to bottom and have very little side thrust play in it, just don't shim it too tight or it will get hung up and you'll play hellz trying to free it back up.