Here are some rearend measurements I have been looking for, hope it helps

[MonzaRacer]

From flange to flange is:

~55" for 2wd ( I believe this is 54.5 without drum/disc but will need to measure my old axle
~59" for 4wd
~63" for ZR2 offroad.
Now if you take off the shelf axles the total difference is 4.5 in wider for the 4wd, allowing only for axle differences from 2wd to 4wd axles.
These measurements are within a quarter inch. the ZR2 is a 8.5" only I believe. The other two are both available in 7.5/7.625" and 8.5" ring gear. The only 8.5" 2wd rear is behind the 4.3L/5 spd trucks. I think in the 4x4 some years with 4.3 got the 8.5" depending on other packages added, like a towing package. All the 8.5's are 3.42s or better gears and posi's. They also are somewhat expensive since they are in demand.

There is also the explorer rear end. Its 60" flange to flange, and 94 and up ones are 31 spine axles. They mostly are Trac-loks, and have 3.55, 3.73, or 4.10 gears. They are also available in both drum and disk brakes and are dirt cheap since every explorer ever made has one under it.

[MonzaRacer]

ttt