I wondered if anyone knew what car to pull a rear from that would fit a 57 chevy.
i really have a problem with the skirts on the outside and small wheel wells...not really into tubbing it out.
The original rear is 54 inches from brake drum to drum on the inside.
I'm thinking any 10 or 12 bolt is fine i'm not looking to race just really need posi to keep those narrow wheels from spinnning when normally pulling out.

 

i'd try this:

http://groups.msn.com/OUTLAWSCARCLUB/555657chevy.msnw

think you'll have better luck there than a 3rd gen f body site

 

My nephew put a Mopar rear in his 57 Bel Air. Leaf spring rears are pretty easy to do.

 

I seem to remember 68-72 GM "A" body rears (Chevelle, GTO, 442, Monte Carlo, etc) are a good fit, you just have to cut off the 4 link brackets and install mounts for the leafs (off your original rear). You might look at 67-70 Mustang/Cougar 9" rears, they're pretty close also if I remember correctly (first car was a '57 Chevy).

 

I've been running an 8.2" out of a '71 Nova since 1998. It's just under 55" wide.

I have a racing bud who has an 8-3/4". It's a little wider, more like 56".

No matter what you do, you're going to have to weld on new spring saddles. I got a pair from Jegs and welded them on. Cutting off the old saddles was a lot more of the work (no cutting torch).

If all you really want is posi, find a posi carrier. They all fit up through '62 model full-size.

FWIW, there's another racer out here with a '37 Chevy PU, runs a Roots blown 383. He uses '57 type rear ends, has welded supports onto the case, and uses Moser axles. The thing weighs 3700 lbs and runs mid-13's up here. He keeps an eye out for those posi carriers, just to have some available for a "bad day" (hasn't had a bad day for the rear in over 4 years).