Hey 426 Dart,
Nice pickup! I mean Dart... LOL!
It depends on how much you want to spend...
Moser sells 8 & 3/4 rear end housings and axles.....
Dana 60s, if you want to spend more...
B body rear ends from 62-70 will require using off set shackles and moving in the spring perches.
I prefer 8 & 3/4 for easy changing of gears.