ive got a similar problem on a -70 bb,when driving nice the clutchpedal returns up,but if i rev it high on 1st gear and put it in second the clutchpedal sticks to the floor for a couple of seconds until the rpm,s come down,then the pedal returns from the floor.not fun.but ive got a diagram pressure plate and the overcenter spring still there.i guess i will try with removing the over-c spring.anyway in my old dc-bible it says that when you step on the clutch there should be a 0.60" space between flywheel and clutch.