Your project is similar to mine. This and other H-body forums have been a big influence on how I plan to approach this problem.
I plan to add welds all around the perimeter of the rear upper mounts.
Next, I plan to purchase a set of the H-body traction bars off of ebay. These bars should take a lot of load off the the upper mounts and control arms.
Also, I plan to install a set of 82+ Camaro coil spring air bags to help tune/adjust how the rear axle reacts.
Finally, many veteran members that run a short tire/small tire (p235/60-15 ET Street Radials), recommend a 2700-2800 stall converter with 383-406 torque motors. (Higher stall speeds are more likely to blow the tires away).
These are the things I'm going to try..... I'm sure that other members, some with time slips, can chime in with suggestions.