where to find 8.75 sure grip units used

im very well aware i can buy a new one. Im just looking to save some money, and I dont know how to set-up the gears, thought if I could find a sure-grip with 3:55 3:90's i could just easily swap them out and save money on labor by doing it myself and not having to "build" the rear-end.


thanks for the advice I'll just check out the vans/trucks/big cars from 60's-70's i guess