Who knows how many rearends Ford made for the Mustang in 66? Was there a smaller one for the I6s?

 

For 66 I think there were only two rearends available, the 7. somthing for the I-6s, and the 8" for the V-8s, as far as available ratios, I am not sure what was available.

The rear for the I-6s is a relativly light duty unit that used the 4 bolt hub design. (4 bolt wheels)

 

I don't know definitively, but I believe there were at least three, the 7.5"(?) for the I-6, the 8" for the A & C code V-8s and a 9" for the K-code.

 

Actually the 6 banger had a 7.25 rear, but you are right about the C, A and K codes. The 9" rears were used in mid to late model Ford cars and trucks.

 

607,568.... one for each car.