Rusty, you've rebuilt a lot of stuff. I've always wondered how many miles are on my 70. Judging by the lack of wear on the pinion flange from the seal, and what I found inside the broken transmission which looked really good except for being broken, I think this is a low mileage truck, but the speedometer has been replaced so I don't know what the mileage is. What would you guess? It's a '70 and I can just barely feel the seal groove in the pinion flange with my thumbnail. Everything I open and look at on it looks pretty new.
That very well could be the original mileage. Unless it had a total refurbish done to it at sometime. But in all reality I only saw a few deuces that had all the differentials and transmissions and transfer-cases replaced. Most differentials last the life of the truck as do the transfer-cases. Transmissions do get the worst of it especially with new drivers coming in all the time.
Check the date on the differentials tag. If they are around 1968 to 1970 then they are most likely original, and with no wear on the flange from the seal then in all likely-hood you have an extremely low mileage deuce.
Yes I have rebuilt a lot of stuff and the damage to my hands prove it ! I have broken my left wrist so many times from hitting it with a hammer when driving out bearings and bushings that the doctors want to fuse it now. I still can move it so I will deal with the pain for now. There are small fragments of bone floating around there that occasionally get jammed but a cortisone shot helps keep the inflammation down.
Your probably wondering why I hit my hands in the first place. Well after working all day on gears and bearings and bearing races you get tired and loose concentration and aim. At one time all I did all day long was rebuild differentials and transmissions and transfer-cases. I got carpal tunnel during that time from swinging my hammer all day long. Yes there is a lot of measuring with calipers and micrometers and dial-indicators but that is after all the pounding and pulling and pressing is done.