I used a 54 passenger car 3:55 rear in my 46 half ton many years back worked sweet. Width is right, you'll have to move spring mountings over a bit and adjust fore and aft to keep it all centered in the wheel well. I wanted to stay 6 lug so stuck the 54 tube in a 48 passenger axle housing. I think I also used a lowering block as passenger car mount to spring is much different.

Jim, I.I. #173
(It's easier to get forgiveness than permission!)