64 Falcon
An 8 or 9 inch rear end out of a 64-73 Mustang would probably bolt right into your Falcon, as they all used basically the same floor pan, and if I remember correctly, a lot of parts like differentials etc were used commonly by both the Falcon, Comet, Mustang, and Cougar of the 60's. I do recall that in 69 or 70, the Falcon here in the US was upgraded to a cheap body model Fairlane, so I am not sure about that time period. My parts interchange book is showing a myriad of differentials for 64-69 Falcons, Mustangs, Comets, and Cougars, and none of them seem to show the same numbers, but that doesnt mean anything either. About the only thing I could recommend is get a tape measure, and measure the distance between your backing plates and also the distance between your spring perches. With a book that has more detail than mine, you could probably find what you are looking for. My bet would be to go with the 8 inch rear end, as they arent as popular for hot rodding stuff as the 9 inch, but they are underestimated, and will take a lot of abuse. Ive even seen them behind stoutly built 460's.
The Granada was a common user of the 8 inch as well.