I've found that a rearend out of a Dodge or Ford van is just about a perfect fit for my 54. The Ford is slightly wider, but nothing to speak of. The Dodge is only about 2 inches wider at most, which is only and inch per side. More than enough room between the fenders. Not for sure on the truck axles but I'm pretty sure they're a little wider even yet. The van axles will generally have more road friendly gears too.
