The 1964 & 65 Falcon and Comets V8's had a 58 inch wide 8 inch axle. The match from that is the 1977 to 1981 Granada / Monarch had both the 8 and 9 inch axles or the Lincoln Versailles 9 inch rear end the bonus is that they also have Disk Brakes.
The next best 8 Inch axle is the 1965 & 1966 Mustang's at just a 1/4 inch narrower than the 1964 & 65 Falcons & Comets and will be a bolt in.
Next best 9 inch rear end to look for is 1957-1959 full-sized Ford & Mercury passenger car's will have a housing width of 52 ¼" across, flange-to-flange (same as 1965-1966 Mustang 8-inch rear end). Plus these rear ends also share the same leaf-spring perch locations as the 1965-1978 Mustangs with a 43-inch distance center-to-center. A direct swap for '65-'70 Mustang will give '67-'70 Mustangs slightly more wheel well clearance. These "narrow" 52 ¼ housings will also fit the '71-'73 Mustangs but wider wheels & tires will be mandatory unless spacers are used with the stock wheels to space them back out.
The '57-'59 Ford big-car rear ends came in two housing configurations a Large axle bearing housing, or the Medium axle bearing housing these are the same bearing size as early Mustang 8-inch rear end).
(1) The Large bearing housings can only be found in the '57-'59 Ford station wagons, in the '57-'59 Ford Rancheros, the 57-59 Sedan Delivery's and also with a little work the *1958 to 1960 model T-Birds 9 inchers.
(2) The Medium axle bearing housing will be found in all the other '57-'59 Ford passenger cars.
Note that *The 1958 to 1960 model T-Bird 9-inch rear ends measures 52 ¾" inches across only a ¼ of an inch (per side) wider than the other early 9-inch rear ends. But it dose have the spring perches at 36-inches apart, so the spring perches need to be cut loose from the housing and moved out to a distance of 43-inches between them and then be re-welded to the axle housing tubes the T-Bird leaf-spring perches are also made of a much "thicker" material. I used a 1958 T-Bird 9 inch in my 1941 Willys A/G build back in 1967-68.
