51 Rear End
I have a 50 Chevy Fleetline.. The first thing to consider for me was the width which I measured to be 60" outside to outside. I ended up using a 73 Camaro Posi I picked up on Ebay. It is a 350 ratio.. I liked that because I want to cruise mostly but get there sort of quick. I also have a 700R4 Tranny so that helps with gas etc.
Just a note.. I have a couple of friends who used 55-57 chevy rear ends with great success... Another that fits is a late model S-10 so you can have disc brakes if you can afford it ....
Get what fits under there. Just keep in mind that you will only be able to use 8-9in tires because of the way the inner fenderwells are made.
I am tubbing a little to fit larger tires under there. Instead of using a cut down rear, I am doing backspacing on my wheels for the larger tires. 10-12 Inches. I narrowed my chassis using a driveshaft loop crossmember and some braces. It really strenghtened up the chassis. If want to see just email me.