I have a 91 RS 5.0 carb. I want to put a perfomance motor in. However, i afraid of braking the rear end. Is there a direct swap that i can install in a weekend without having to modify. I am new to chevy and dont know anything about them.
Thanks,
Chris

The only strong bolt in rear ends are the Moser and Strange 12 bolt and 9 inch Fords. I like the 12 bolt best myself. These rear ends start at $2220, so they are not on the cheap side. They are VERY strong. There are no other strong rear ends for these cars, except the very rare Dana 44.

As for a junkyard diff, you already have the strongest one that will be a direct bolt in. You're not going to find any other junkyard diff such as a 9", 12 bolt, etc that will directly bolt into a third gen because of the torque arm suspension.

You best choices are an aftermarket, direct bolt in 9", 12 bolt or Dana 60 but expect to pay over $2000 for a complete, ready to bolt in diff.

If you do manage to find a third gen Dana 44 that's in good condition, it can be just as expensive as an aftermarket diff. The Dana 44 was never in a production vehicle. It was only available over the counter from GM and was in the SLP Firehawk.

Wrong....

The Aussie 9-bolt is a bit stronger than the 3rd gen 10-bolts. Then there are the 4th gen 10-bolts.

What makes the 4th gen versions is the posi unit in the middle. Blowing up a 3rd gen posi was generally the first part to go, before the c-clip axles (which the 9-bolts don't have).

Although 9 bolts are marginally stronger, they were only available for a few years and parts are expensive or hard to find.

A fourth gen diff is no stronger than his 1990 diff. They use the same size ring gear and axle diameter. Using a different type of posi doesn't make it any stronger.