Update and newly discovered info - may cause me problems
I found the tag on the axle and it is a Fayette axle with no info on axle load size except for a series of numbers that look more like serial numbers ( company code indicating load ? ). I speculate it would also have Fayette brakes/drums. They don 't look like Dexter but do resemble the few pictures I have found of Fayette brakes/drums. Company no longer exists but may have been bought out by dexter. I have read that Fayette may have used now obsolete bearing sizes.
Now I 'm wondering if Dexter backing plates and drums will even match up bearing size wise for spindle. Guess I 'm gonna have to call Dexter and get voice help. I much prefer that as apposed to stumbling through their web site with my obvious lack of knowledge. Sure hope I don 't have to buy a new axle, backing plates, and drums. Not to mention the trama of removing old and installing new in a safe manner. Dad once told me if I can 't lift it by hand, don 't crawl under it.
btw, is there a way to weigh the rig short of taking it to a scale ?
Looks like you are well on your way (-:
(to becoming another "History detective")
According to the age there may have been industry standards in place at the time.
I do know that bearing size standards (and numbering/designation system) have have been in place for WELL OVER 50 years.
As far as weighing it without taking it to a scale;
There is (what I regard as) an urban legend that you can "accurately" measure tongue load with a bathroom scale, a short board and a couple of short lengths of black pipe.
Yeah, it looks good on paper, but in reality things on pipes DO roll (hence the term "pipe rollers" for moving heavy machinery).
I don't like the idea of some small number of hundreds of pounds coming at my ankle from a foot or so away, i.e. I probably wouldn't react quickly enough.
So yes, in theory at least you could measure the load on each wheel using a bathroom scale rigged up as one end of a bridge and the wheel somewhere along it.
Probably not worth it, a guess of 85% of the tires' rated max load is probably close enough for everything you are doing (-: