I am going to be purchasing a powertrax no-slip locker and I need to know what size rear it is....I have an 88 camaro w/auto. and 2.73 gears. Powertrax makes a loker for the 7.5" and 7.625" rears....what size is mine? or are they the same?

Same.

It's the same size unit, but the spline counts are different. With an 88 you probably have 26 splines. I think it's some 89s and all 90 and up that have 28 splines. Make absolutely sure before you buy the powertrax. Best to check the front of the passenger side axle for a code stamp and look it up.