Which used rear should I look for? Ford 8.8, GM 8.5 ...?

[crakarjax]

I recently realized that the 12-bolt truck rearend I was going to use on my project is shot. So I started looking around and can't really tell which rear would be best for me. People say that the ford 8.8 is a good fit and I have also seen some rearends out of S-10 Blazers on craigslist. Also saw some members using Impala/caprice rears. I am mostly concerned with the width being correct, but if I am going to buy one I figure I might as well go for one with disc brakes as well.

What models/years should I be looking at for donors? Is there a website with dimensions that I can reference?

TIA