I have been chasing this knocking/clunking noise for awhile in my car. The setup is 1995 firebird, LT1 with a comp cam, RAM powergrip clutch, fresh t56 rebuilt by tick performance, Strange s60 with 4.10 gear. When letting the clutch out from a stop or when shifting at part throttle I get a knocking/banging and I can feel it in the floor of the car. Shifting at WOT feels fine. Its not clutch chatter, I've felt that before. This is a clunking that I can feel in the floorboards. Ive put thousands of miles on this setup and never had an issues racing or on the street, just this annoying clunking. Ive had the car up on jack stands and I cant find much slack in the driveline and cant find anything hitting or interfering. Here is what Ive done so far

poly motor mounts both good
new rubber trans mount
poly torque arm bushing good
torque arms bolts tight
checked flywheel, bell housing and pressure plate bolts
pinion angle at -2.5.
u joints are tight
flushed the clutch fluid. never had any engagement or shifting problems anyways.

The clutch feels fine and the trans shifts fine but has a bad knocking sound.

any suggestions?