1970 Mustang = Leaf Spring
1993 Mustang = Unequal length control arms and coil springs.
1970 Mustang = Big fat car w/ wide rear end
1993 Mustang = Much narrower on both counts
Way to many Fox length 8.8's out there that bolt right up to be messing with an 8 or 9 inch. Besides, it takes more power to work the ring and pinion of a 9 inch than it does a 7.5 or 8.8 due to the position of the pinion gear in relation to the ring gear. It's that same relation that makes the 9 inch as strong as it is. In the 4cyl, world, turbo or not , a 7.5 will do, and an 8.8 in most applications is overkill.