Choosing a rear suspension

It is IMO that a good move would be to relocate the springs inboard for max tire width. (Which I suppose you know about and your doing.) Look into “Viking” shocks on all 4 corners. Users seem to love them. Sorry, no practical experience with them.

There is a reason SS springs are the way they are and not 1 spring for both sides.
Yessir, I have already done the spring relocation into the frame rails along with a mini tub.