I'm building my 76 camaro, so with more power I want to build the rear end. Does anyone know of a strong durable rear endthat will go in. Right now it has a 2.56 or something.Will a 3.73 fit in or just swap out a whole ford 9' rear end.

The 8.5" 10 bolt like you have will withstand a lot of abuse, provided it's in good shape. You could break it with a standard trans and slicks, but an automatic/smallblock will probably never break a good set-up 8.5"10 bolt. Gear ratio depend s on what you want to do, but parts are cheap for that model 10 bolt.

Which is better a 7.5' or 8.5' rear end?

another i dea i just replace your stock gears with somethin a lil beefier like 4:11's they are strong and they have a goo acceleration time, thats what i have in my 76

stay with 8.5", get c-clip eliminators w/ superior axles, they are strong, and affordable.