So what happens if you keep the old /6 rear end after 360 swap?

My 73 Scamp came stock with a 318/904/7 1/4 I put on a 4bbl and a set of side pipes, drove to the carwash, washed my car, pulled out of the carwash without getting on it I just pulled out onto the road and KACHUNK!!! I limped it home and found a 8 1/4 at the local yard.