rebuilding previously bagged rear setup...help

[bigbeardedbastard]

i recently picked up a 85 crew cab dually that is already bagged....the workmanship is poor and it drives like crap. need some ideas on what i can do to change it....

a breakdown of the issues i have with it

the bridge is horrendous looking and even though its done in 1/4" or thicker plate it appears to only be welded to the outside of the frame rail

the rearend hits the front of the bridge when dropped due the the really crude homemade 2-link set up. there is no adjustability and they even welded the axle to the bars themselves. i would like to change that as well just dont know what most would recommend. i dont plan on towing anything more than a bumperpull single car trailer but have read a ton of threads where ive seen parallel 4-link, triangulated 4-link, 3 links, 2 links....i dont know what works best?

also bag placement top of axle, inside of rame rail outside of frame rail??? its just going to be a cruiser and occasional hauler. with the 350/400 combo im not drag racing or autocrossing

shocks? the PO didnt even install shocks on this truck. i know this topic has been beat to death but im struggling to find the answers i need.