Got a lot done the last couple weeks. Got the rear end put back together (last time I ever go with a 9 bolt) mocked up everything and plumbed some temp air to see it cycle and set up sensor locations. Cycles great. Looks like the lift is decent and it lays until it hits the old leaf spring hangers which is right where the rockers sit.
https://youtu.be/t_qbgB3-vwo
https://youtu.be/CpQJoyhjcCQ
Heres a few shots of how the headers fit. Close in a couple places but didn't have to trim anything. These are speed engineering c10 ls swap headers. Looks like I may need to heat up the coupling and just dent it in a bit because it hangs about 1/4" below the leaf spring hangers.