rear axle question?????

I have a 72 Valiant 4 door project that I am starting. It has a factory 318, 904 trans (i believe) and a 7.25 rearend factory. I was kindof shocked to find the weak 7.25 from the factory with the 318. Any way I want to upgrade the axle what is the best car or truck to get the axle from at the junk yard? I am keeping the 318 for now but may upgrade to 360 later. I am building this as a cruiser so the motor will not be overly built maybe a few bolt on for some stop light to stop light fun. Thanks in advance.
Bryan