Well, if you look at some of the DSM's running 500hp, they have the stock 4-bolt rear diff......So it should be able to take at least 250hp.

Why didn't you look for a Corvette chassis? The '84 and up vette's sell for pretty cheap when theyre smacked-up, and that diff can take 500hp (its a mid-sized Dana I believe).

What car is this going in?