axle swap on a suburban 4X4

[jonzcustomshop]

my dads 1990 1/2 ton suburban has a shot front axle... our cheapest fix is going to be to just change it out.
since it is a 4X4 I will just swap front and rear to make sure we get matching gear sets...
we have 2 parts 4X4 suburbans that we can use..
an 86 1/2 ton, and a 90 3/4 ton.

I just want to just switch both axles onto the 90, so I am wondering if the 86 will be a bolt up deal, and if not would the 3/4 ton 90 be a better choice?