So I ended up putting all the LS swap related stuff in a separate thread in the engine subforum.
https://67-72chevytrucks.com/vboard/...d.php?t=806095
This week was pretty busy on the next phase.
Belltech 3" drop spindles, flip kit, new 3/4 ton springs to cut down.
Not pictured, UMI rear shock extenders and a new Borgeson steering box.
I posted some pics elsewhere and had a bunch of people asking "why not just buy lowering springs". Scotty Baccus who runs the LS swapped squarebody page on Facebook lays out the case for this method.
Short version is: Modern vehicles have a spring rate of like 12-1300. Stock C10 springs have a rate of like 6-700. Aftermarket lowering springs for C10's also have a rate of 6-700, they're just shorter.
A C20 spring with a thicker coil wire (0.82" vs 0.78" for C10 spring) has a rate around 1200.
So in theory trying to match a modern spring rate for a better ride.
I don't know if that's all true but his advice has helped a ton on the other work I've done so I trust him enough to try it.