Fords - Which power steering boxes can take a ratio upgrade?
Some Fords, from 1965 to 1979 (Mustangs from 1971 to 1973) used Saginaw gearboxes, but not all of them. Those with Saginaw power steering gearboxes can be upgraded to the 12.7:1 ratio.
It's easy to tell if you have a Saginaw box in your Ford. Saginaw's have 4 hold-down bolts on the adjustment cover, the Fords have 2 bolts on that cover. If you've got the 4 bolt cover, your gearbox can be upgraded to the 12.7:1 ratio. (click the image to see full size)
Saginaw Gearbox - with 4 bolt cover
Ford Gearbox - with 2 bolt adjustment cover