73 Dart Rear End Swap

My grandpa also has another 8.75 that is out of an E-Body (old mopar guy with ALOT or parts!) only problem is it has 3.23 or something and it's open diff I'm pretty sure, still heaps better than what I've got. I was hoping not to have to shorten it but if it's so cheap I may as well just do that and then I'll have brakes that work and everything. I'm going to rummage around and see if he doesn't need some stuff. He has an entire sea-can full of cuda parts, shells, and a reinforced ford 9 or something, and ANOTHER 8.75, I probably have the available parts to put together a rear once it's shortened.