Dump the "Flow Stoppers" and get some straight through muffs for better WOT like the Magnaflow 14x7 with 3.0 side inlets with the 3.0 inch center outlets and mount them behind the rear end for better sound and performance over your current set up
You may want to have a low gear set (2.70 or higher) installed in your tranny instead of using a lower gear ratio in the third member, way better for launching and cruising also
That or buy and use a later model O.D. tranny for that car with a lot steeper low gear and adapt it to your motor and car
IHTHs
Mama racing with you is a good thing