I found the 4:11 ratio rear end with an ad right here on the bolt. These rear ends 'center section/pumpkin' comes out as a complete unit once you have the axles pulled. Difficult part is finding one. You need to get a shop manual and study that to get a grasp on what's going on with these trucks.

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed