I have a 72 SS, I just bought and dropped in the 340HP chevy create 350. That parts runs and is wonderful.
But this car is a DOG in terms of body movement !! Its literally like a boat on rough waters.
This car has front and rear sway bars, air shocks in the rear, and upper control arms for the rear-end (not sure if they all do???)
Anyway, If I replaced all the bushings in the control arms (rear) and body mounts. Do you think this would solve some of this.
I know that shocks would mean alot but do I air shock again or go with some high preformance ones?
In other words, was is a definate fix and what is a relative modest budget fix?
Any info would be appreciated.

Yes, I think replacing control arm bushings and body bushings will help if they have never been replaced. I think the air shocks are causing part of the problem, especially if they are used to jack-up the back end of the car. (FYI air shocks are known to cause breaking of the upper shock mount).

If the air-shocks share the same lines, both shocks will always have equal-pressure, so when you load one side (when cornering, the weight shifts) the pressure added to that side forces more air to the other side, making the body-roll even worse. This is very noticeable if you have a lot of the car's weight riding on the shocks rather than the springs.

If you really want to run air-shocks, valve them separately.