Ok im needing a gear change and a new posi. The rear end is going in my 81 with a 383 im guessing somewhere between 400 and 480 hp at the crank. The car will mainly be street driven track maybe once a week.

Should I?

1 Rebuild stock 10 bolt
2 Find 12 bolt and build it
3 Find a ford 9" and build it

Im kinda leaning to a 9" do to not haveing c-clips.

For that horsepower i think that the 10 bolt will be strong enough. That would prolly be the cheapest way to go. But if i were to rebuild a rear end id want to build a 9 inch its something that should hold up forever if its build right so if you put in a bigger motor it'll be fine. And i think that the strongest rear ends came outta pickups and full size cars i have a book that says that anyways i think.
I would get a 9 inch with disk brakes then ur all set man.

The 8.5 10 bolt is a strong rear end, but it can be made stronger. You can install a 30 spline Eaton posi with 30 spline Moser axles and you have a rear end that is close to the strength of a 12 bolt. There are many versions of the 9" Ford and getting the right combination of parts can be difficult. It also takes a little more power to turn the 9", and it is heavier. The only 12 bolt that will fit your car is the '70 Z28 or SS rear end. They are a little hard to find.

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead (http://www.lubedealer.com/biggearhead)

I have an 81 Z also with a 383 and about 475hp with 10 bolt.September we put in an eaton posi with 3.90 Precision gears and bearing and seal kit,with installation it was $1000.00.Alot of money but what a differance.It really woke up the car.Was told to put 500 miles on it to break in gears,can`t wait to get a time slip.

Hey biggearhead what do you think about c clip eleminators for the street? necessity or not?

Most of the time they are not necessary on a street car. They tend to leak when driven on the street. If you think you need them then put them on, don't rely on what I say.

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'69 RS/SS396 Pro Street
427 4 speed 9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead (http://www.lubedealer.com/biggearhead)