I found a 12-bolt that a guy is practically giving away... I was wondering what do I need to do to make it fit my car? I think it's wider than my stock rear-end so I would need new axles after removing the extra lenght I guess... anybody know if there's a guide for doing this? Can it be done?

 

The biggest problem is the lack of the rear mounts for the torque arm. I know someone who converted a "non torque arm" car 12-bolt to work in a 4th Gen, narrowed it, etc. Although he saved a few 100 $$$ compared to buying a new one, when he was all done and running it, he said he would never do it again.

You would have to consider these questions:
-does it have a limited slip differential?
-does it have the gear ratio you want?
-does it need a rebuild?
-will you have to change the end plates for 4th Gen the disc brakes?
-does it have C-clip eliminators?
-width - narrow axle tube and buy shorter axles
-add torque arm mount
-remove all old attachement hardware and replace with stock hardware from your stock 4th Gen axle (LCA mounts, panhard rod mount, spring mounts, shock mounts).
-Does it even match the GM "car" 12-bolt? The GM "truck" 12-bolt center section is not the same shape as the old GM "car" 12-bolt..... will it fit in the available space? The "truck" 12-bolt has a smaller diameter pinion stem (1.438" vs. 1.525" for the car version)
-how strong are the axles (how many splines)
-how strong is the pinion yoke? What size U-joint?
-what length driveshaft will it require?