I hope this is the right forum for rear ends

I have a Dana 44 under the back of my '65 Studebaker Commander. I'm working on building a street performance engine for it, say mid 300hp to 400hp (not all decided yet).

It has 3.31 gears with no posi or locker or anything. With that hp I'm thinking I need both wheels turning and maybe different gears.

Can I get new guts from any Dana 44 to put in it or are there differences between car mfr's and years?

What gears would you all recommend?