Well i found out 9" can be posi only if it comes in 31 spline.

Now the questions:

1) which posi is the strongest. Eaton or Auburn

2) How much power can a 31 spline hold.

Right now i have stock shortblock a lot of bolt ons and hot cam for now. In the new future i will be working on a hopefully 500fw engine with 200 shot of gigly gas, so will a 31 spline hold up to slicks and 5000 clutch dump?

I know if it does i can alway switch out the internals of the 9" and convert to detroit lockers, if it comes to that :

 

well, the Auburn and the Eaton are both good units. We have a El Camino that runs 9's, and iit has 31 spline axles, with spool, and 33x18x15 inch slicks. The 31 splines are doing just fine.

 

have you found a 9 inch that you can put under the the f-body for under 1000 or so?

 

i wish i could find a rearend that was under $1000. I'm sure it can be done but you have to be in the right place at the right time to catch the deal. or know someone who can do it.

 

*shrug* my 9" cost 1300-1400

 

If you build it yourself you can do it for right around a grand depending on the parts you want to use. I'm finishing up mine right now...