88 3/4 ton suburban axle shaft the same as a 88 1/2 ton?

[jonzcustomshop]

looks like the u joint is wiped out on the axle shaft of the 88 3/4 ton suburban front axle I am using... I have a "parts" axle out of another 88 sub, but it is a 1/2 ton... any chance that they are the same?
both axles have a 10 bolt cover, and for all I can tell look the same except for the different hubs...
both are the manual style (you get out and turn to "free" or "lock")

this is the short axle shaft that has the bad u joint.

or? would it be just as easy(or hard) to just replace the u joint on the current axle?