[Old H2S]

Some back ground..
I am Old Fart, I have done this before on many cars. Over Kill is my middle name.

My new to me 83SC has 300k miles on it and has had 2 major impacts to it. The first in the drivers side front fender that was repaired but the car is out of true on the diagonal with the front main cross bar 6mm back on the driver side causing miss alignment on both door closing. The second hit was a snap over steer impacting the drivers rear wheel.
I will pull the engine to get the frame aligned.
The big question is, this unibody car is soft, and flexible still after repair, what are the best ways to firm it up without getting too much NVH ?
I usually make up custom sub frame connectors..and stitch weld the spot welded panels, build roll bars, shock mount reinforcements. Then when you add all the handling upgrades you are "down the rabbit hole" and have an upgraded brick.
What are your opinions?