I looked through old posts but still don't know. I have two differentials. One has a R2 0148 on the axel shaft and was in a 1971. The other is in a 72 and has 407298 on the main case but axel shaft numbers can't be read. I need to end up with a posi and 3.23 or 3.42 gear for my car. Want to use a 4 speed manual too but don't know m20 m22 etc.

 

R2 is a 2.56 ratio, and I think an open diff.

 

2.56 open. No where near where I want to be.

 

Anyone know what the other rear end is by the case number?
407298.