The Stovebolt Site Forums The Shop Area Driveline 53 - 54 frame differences

Jim Carter - tech article.
Rear Axle Bumper Change
Error: 1st picture should read 1947 to 1953 instead of 1954 to 1965

More of the same.
Overload Rear Bumpers

The 54 frame flattens out over the rear axle to accommodate the deeper bed.
Engineering features (courtesy tclederman)

Cross member changes
Rear Engine motor mounts (courtesy tclederman)

I think you would run into problems if you put a 54 bed on a 47-53 frame. The 54 bed is 3 inches taller.
As oppose to putting a 47-53 bed on a 54 frame, the 54 frame arch at the axle is lower.

Rear axle bump stops on 47-53 frame are mounted under frame arch.
Rear axle bump stops on 54 frame are mounted on side of frame.