8 1/4 from a '73-'76 A body is big bolt pattern (4 1/2") and is a bolt-in. Any A body 8 3/4 will bolt in, but (stock) you will have the 4" bolt circle, but big bolt axles are available- but those require B/C body brakes.
Ford 9" out of a Muskrat/Maverick/Comet I hear is a bolt-in. 4 1/2 bolt circle.
Ford 8.8 out of an Explorer fits with some minor work: since center is offset, you shorten the long tube to match the short side and use two short axles. Cheap, plentiful, and with smart shopping gets you good gears, limited slip and disc brakes.
All the above get you stock (or damned close) width rears.
B body rears are a little wider than As (there are variations in years), the perches are off by a half inch or so per side.
Big B, C and truck/van 8 3/4 rears can be narrowed to whatever width you want. Same goes for truck Dana 60s.
All depends on what you want (small BP, large BP, stock width, narrowed, etc.)and how much you want to spend.
LOTS of threads on here about all these options, search and read.
