Buying a new rear end

So i am in the market for a new rear end for my 67 Monaco

found a guy selling a 8 3/4 for a "c" body for $200

what should i look for on it to make sure it fits?

i know my car came with a 8 3/4, but i would rather spend $200 on a new rear end with new bearings, seals, and studs, then replace al those same things in mine.


thanks

tom