In the order above would be my first choice. Tri-five chevy is a bolt in also i believe. Might be Cheiftan that im thinking of.
What ratio do you have now? Common gears were 3.32:1. Gears from 48-56 will all work but you may have to use different pinion bearings for the earlier gears.
I belive its 3.42 gears. I looked the stamp number up in my book. the number was 8 on the housing correct me if im wrong about the ratio for that number.
Cheaper to set up gears than do a whole rear no? 55-57 Chevy should bolt in, 57 olds/pont should bolt in. Might be able to use early Camaro rears as well. I think the pad spacing is the same or very close.
measure the distance of the spring pads. make sure the shock mounts are im the same locations. the wheel bolt pattern will be different. yours is 5 on 5"chevy is 5 on 4 3/4". you will also likely need a conversion ujoint as yours should have a flange type.