Most of the information here is correct. I would guess that 90% of all V8 Mustangs originally came w/ the 8" rear. Only the Hipo's or cars with a 351 or larger engine ever got 9" rear ends. The I6 cars actually came with a 7.5 inch rear that used 4 lug wheels. I have to say that the best improvement that can be made on one of these cars, regardless of ring gear size, is to change that rear gear to something more performance oriented. On my current car, I only changed from a 3.00:1 gear to a 3.40:1 gear, a small change, and found response to be MUCH better. I can only imagine the difference to a 2.80 geared car going to 3.55 or 3.89 gears would feel.
