While searching for a reasonably priced rear end up grade for my g-body project, I found out that you could get a 30 spline 8.5" 10 bolt in the 96 up s-10 V6 blazers. The 2wd's are 54" wide the 4wd is wider (58" I think) & the ZR2 option was even wider. They are all available with 3.42's & the ZR2 was available with 3.73's. Because of the upper mounts they won't work for me, but they should not be too hard to adapt to an F-body.
This is all from what I read so measure & verify before you buy.

 

Do they have a torque arm mount? LCA mounts? spring perches?

 

No, they are setup for leaf springs, but a decent fabricator would be able to adapt it.

 

be careful not all are 3.42 and not all have a posi, i got lucky my 2000 s-10 came with an 8.5 rear but with 3.08 gears and an open diff. it is hit or miss finding them and usally they are a little pricey, the zr2's are the widest. and would most likely work the best on an f body.

 

How wide is the f-body axle? I thought it was around 54" or something.

 

i'm running a late 70's early 80's 8.5" 10bolt that someone welded the tq. arm brackets and lca's stuff... let me tell you, that is a nice heavy duty setup!

 

How much did it cost you to get the needed stuff welded?

 

The ZR2 8.5" rear axles (at least the later ones) were all 3.73's with an Eaton locker.