The 3.55 R&P gears conversion is not a change to a 1954 rear end. The 3.55 rear end was not standard in an 1954 1/2 ton truck.
My 1954 3100 trucks have been converted from the original 3.90 rear end to the 3.55 rear end.
I also have tires on original 16" wheels that are about 10% larger diameter than the original tires.
To compensate for the speedometer error from the 3.55 and the tires, I use an adapter from The Speedometer Shop. My speedometer/odometer now has less than a 1% error.
http://speedometershop.com/rep-pag.htmI think that Jim Carter also sells an adapter at a good price.
