Plymouth duster rear suspension questions

I’m running the Firmfeel HD springs, 1 inch lowering blocks, dual position front spring hangers on lower hole and the FF over axel sway bar, pinion snubber with billstein RCD on 225/50-16 Falken 615’s all around with 392 HP at the crank in my current mellow 340. The front is FF tube upper arms, plated lower arms with the FF stock style sway bar and RCD. Car handles awesome in the twisties and sticks. The one thing I’m going to add at some point in a panard bar to the rear to stop any side to side play.
As the other guys said, the 3in spring relocate is a drag race thing not road race. From looking at the factory AAR/TA road race cars that currently run with historic TransAm, they did not move the springs, only added a panard bar and reinforced the torque boxes / rear spring shackles. They did some other trick frame stiffening things when the cage went in like 2x1 box molded it across the inside floor pan rail to rail in 5 places to help stop frame twist…