Just thought I’d ask before I depart on this endeavor. What’s needed to put a Mustang 8” in a 56? thanks!!
Early Mustang 8 inch (65 66) have tapered axle tubes at the outboard ends that require different u-bolts and the mounting plate that goes under the spring will need to be modified as well. The width of 65 66 axles (wheel mounting surface to wheel mounting surface) is narrower than 67 and up housings. If I remember correctly, 65 66 are 57 3/4 inches and 67 and up are 59 1/4, the spring mounting perch is the same on both. I used a 76 Granada axle on my 55 Fairlane because the overall width was closest to the original, the springs pads bolted up without issues, same width. The center of the axle (hub?) where the wheel bolted on was larger than my original wheel center so that caused a bit of an issue if running stock wheels. My memory also seems to remember Mercury using 5 on 5 inch bolt pattern, no 8 inch axles used that pattern. The rear u joint from the stock 55 driveshaft would not bolt up to the yoke on the 8 inch but they do make u joints that will bolt up. This is based on my 55 Ford, not sure if the Mercury is exactly the same
my rear I am hoping to use is a 67 Mustang. I’ll definitely have to change wheels for sure. I guess I’m really wondering about the spring perches. That something that needs to move?
I put an 8" from a Maverick in my '54 Ranch Wagon. 56 1/4" WMS to WMS. Had to move the spring perches. The rear axle register on the Maverick rear is larger than the stock wheels so I had to get new wheels. The emergency brake cables from the wagon worked in the 8 inch.
On my 55 Fairlane the spring perches were fine. I did need some different u bolts because the spring perches on the 55 rear end were TALLER then the Granada 8 inch spring perches. T tightened the stock u bolts up and I thought it was fine, took it for a drive and all kind of bad noises back there. Jacked up the car with a jack under the axle and you could see daylight between the spring perch and the spring. The nuts on the u bolts were tightening up on the thread and gave the impression they were tight! Another 1/4" longer thread and they would have worked fine.
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