50-54 powerglide cars had the 3:55 gears. All you have to have is the tube/center section, but you can swap the entire rearend if you prefer. Otherwise a new set of gears can be had from Patrick's. As for other parts, it would depend on the condition of the parts. Bearings may need to be replaced. You might want to consider upgrading to the Bendix type brakes 52?-54.
Get a shop manual and study it.
