I have an 8" from a Maverick under my Ranch Wagon. At 56 1/2" WMS to WMS I believe it's just a bit narrower than a Mustang unit.
No… an 8” is a nice replacement for a 49-56 stock rear and get some higher gears and not race it. It also fits where after 1959 . . . 9” rears were too wide. Today 8.8’s are cheap modern and everywhere with disc brakes.