John Z is correct except for one thing the 6 cyl's came with the 8 inch the only rearend ever smaller than that was the 7.5 and also sometime in the late 70 to mid 80's they had a 6.5 the played with but I don't think it ever really made the street in enough numbers to worry about all the 64-69 had either the 8 or 9 though that was the only rearends made/used for ford in the passenger cars at that time.
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