I have a 1995 Z28 Conv M6, and when driving over rough pavement, there is a loud clunking coming from the center/rear of the car. It sounds like something contacting the floor. There are no whitness marks in the trans tunnel, and no visibly broken parts. I have a poly trans mount that appears to be in good shape. I replaced the torque arm bushing with an energy suspension poly replacement, and that did nothing to help. It is expecially bad over large bumps, and when driving over bumps during a turn. Any ideas??? thanks

Probably the exhaust system hitting the center cross support....... I know mine did...

Might check for worn suspension bushings on the rear LCAs and panhard bar. The rubber deteriorates with age and you could have a metal on metal condition. Also check for loose bolts on the suspension parts.