If indeed that rear end is the stock 'as supplied' by Ford in 1951, it will survive only if you are gentle. It was built to handle 239 ci, 100-110 Hp and 150-160+/- lb ft of torque all put to the road on skinny 'un' grippy tires. In my distant past, I was able to destroy several with just a warmed over flathead and even more when I went to a 312 ci 'Y' block - but they were cheap then and I always had a couple spares along with at least one transmission. Minimum I would consider would be a Ford 8", even better a 9" of a good width and ratio. An 8.8" might be an even better choice, along with the disc brakes.