[Idhomustang]

First ask yourself a few Questions.

1. What are long term plans?
2. What do I expect from the rear end?
3. What conditions will the car see, track, street, highway,roadracing course etc?
4. After answering some of these you will have an Idea?

1. Less say that you plan on the car eventually becoming a drag car, you might consider, installing 4:10 gears and 35 spine axles with a upgrade to the ford 9" axle bearings and seals.
2. You might expect the rearend to handle 1500 hp, in that case you might want to have a professional rebuild with all the good stuff installed, spool, axles, gears all new bearing a reinforced cover with studs, maybe have it narrowed 2" overall for additional tire clearance.
3. For me it would be drag and street use, with some limited highway, so 3:73:1 gears were a good compromise, I run a spool
4. 4 lug axles in the stock 31 spline configuration.

The logic should always be used with both long and short term goals in mind, maybe you can only afford gears, and a mini spool, maybe your car already has 31 spline axles, or a good alburn unit installed already.
Put some good thought into what you want and go for it, I think once you plan well you will execute well and everything will work out in the long hual.

Good Luck.. Mac.