Do you have a matched set of tires front and rear? Are they worn the same?
I have heard stories of people putting the wrong ratios in when swapping front/rearends. Most of the time the truck acts crazy in 4wd when this happens, but you never know.
I've had 4 sets of tires on this truck. Stock, 38.5x15 and two sets of 35x12.5. All have been the same size and model on all 4 and no abnormal wear, the last set were brand new and this would be the second case broken with these tires. I usually rotate them whenever I have the wheels off for anything. Axles are both 3.55:1, I've seen trucks with different axle ratios, they won't move when things are locked. Maybe if you really tried but things would probably break right away on anything but wet ice.
This 208 seems to be working still, but I don't have much faith in it. Shame the 4407 doesn't have a speedometer drive, it looks fairly substantial from the outside and I wouldn't mind running a flange.
IDIoit, why not run the slipyoke in the shaft? One of the reason I hate slipyokes, particularly without a carrier bearing, is you can't drive on the front if you break the rear shaft. I had several ujoint failures with 1330 joints, none with 1350 though they seem to wear quickly so thinking I should have gone 1410. Regardless, I've had to take it easy on just the front a couple times just to get it home before I upgraded.