57 is too narrow - it fits the 64-66 Mustang. 58 and 59 Ford Fairlane will fit the Maverick and Comet. The Lincoln differentials are easier to find than the old Fairlanes.
How is it too narrow? The 64-66 Stang rear is wider than a Maverick. There is someone here that knows about the early Ford 9" rears. I believe it is Mavaholic. The car, wagon, and Ranchero rears are all a little different IIRC, he knows the ins and outs. I am pretty sure it is 57-59 housings that are the same, and they fit an early Stang perfect, but are slightly wider than ours. Some places I know for sure to get a bolt in 9" (perfect bolt ins, but all wider to some degree): 65-66 Stang (rare) ~1" wider overall 67-70 Stang ~3" wider 71-73 Stang ~5" wider 75-80 Granada/Monarch ~1.5" wider When using any of these rears, you must pay attention to the backspace of your rear wheels. You may or may not need to get new wheels with more backspace, depending on your wheels and exactly which rear you decide to use.
As Ratio correctly stated, '57-'59 housings are the same width. They are also the same width as the WIDER THAN MAVERICK '65-'66 Mustang. I have one of these too narrow rear ends in my Maverick. It was a bolt-in with no problems. The wagons and Rancheros had larger housing ends for bigger bearings. These cars also had larger brakes. The parts book shows slightly longer axle shafts for the wagons & Rancheros, so I am guessing that the wheel mounting flange on those axles was offset more from the bearing surface to accomodate a wider brake drum.
I did the 57-59 deal over 20 years ago in one of my other Mavericks. Like stated about the width, I used Centerline 8.5" rims with the 4 7/8" offset (to the inside) and had L60-15" (whatever they relate to now?) And it fit great!
Decent thread: Has all the links that I would suggest you see, but wrapped up in a nice bundle... http://forums.stangnet.com/showthread.php?t=656567
