Dennis,
There is only one ring & pinion conversion option for an enclosed drive shaft 1/2 ton 1947-1955 GMC/Chevrolet truck - the 3.55 gear set from Patrick's (other vendors also sell this set, but it comes from Patrick's).
This kit converts the original 47-53 4.11:1 enclosed drive-shaft rear-end to a 3.55:1 enclosed drive-shaft rear-end. For 1954 1/2 tons, which have 3.90:1 rear ends, a 47-53 ring-gear carrier is needed - but the same 3.55 gear set is used (an enclosed drive-shaft was still used on 1/2 ton GM trucks in 1954).
Patrick's also sells an installation kit - in my opinion, this is a necessity.
Tim
