Rear suspension setups

The factory SS springs are designed so that the rear of the car rises on a hard launch planting the rear tires intonthe pavement. If you are using stock length A-body springs, they are most likely reaching full extension causing your problem. Mopar Performance used to sell longer shocks which were probably repackaged C-body parts. See Fate"s comments above. That would be an inexpensive change to get you going.
But really, if you would rather have a better all around driver, SS springs are not a great choice long term.

Blue car in Statesboro, Ga? Man you gotta have them Stateboro Blues.