Oddly, apart from the housing…

Let's put it this way. If you have a 66 8", and you want to move up, get a 9" diff and 9" housing. The brake assemblies, and even the 28 spline axles will slide right onto the new 9" setup.

OCHOHILL- You found a 9" housing the correct length for a 66? The only one that was actually correct was the one used on 64-66 K code 289HP Mustangs. A very rare bird. You could just get a Currie 8" Traction-Loc, if their figures are accurate it's stronger than a lot of stock 9" rears. That'd save you a lot of trouble. You can get all sorts of 8" gears, too.

One thing you could do right now is install Traction Master bars (not the cheap repros, either) cost a little over $100, and give dramatic results. Then, if you change the axle later, you'll already have them.

 

I found a 9" the correct width for a 66. The guy I bought it from was a shoe box nova guy. Appearently, chevy guys can take this rear end and it bolts right up to many GM cars. Correct width, spring perch location-everything. The tag on the rear end was not for a 65-6 mustang, but the housing jives.

I did not know the 8" stuff will bolt up. I had to buy a moser axle for the old 8" rear end. Is the moser axle stronger than a stock 9"? Should I swap it for the stock 9" axle?

Both housings are 28 spline small bearing end, btw.

I am currently looking for a used center section with a traction device and taller gears.

 

I have a 9 inch, 31 Spline Detroit Locker in my car and want to replace it with a clutch posi. It works fine, but I drive around town (don't drag) and it's overkill. I will sell it for $400 or swap with a 9 inch posi.

 

Ooops, for got to mention 3.89 gears in the det locker.