On the CB750's there were three more-or-less distinct clutch configurations.
Type A (K0,K1,K2):
Is the original and might be called the "Extra disk short basket design"
This design has a slightly larger clutch disk at the base of the inner basket and was notorious for chatter - probably because the springs were weak and the plates and disks did not have sufficient rigidity to dampen vibrations.
Type B (K3, K4, K5, F):
Might be called the "Sprung short basket design"
This design removed the extra disk and strengthened the springs. Chatter was much less evident.
Type C (K6, K7, K8, F2):
Might be called the "Long basket design"
Longer basket and internal parts, longer and stronger springs, and a double rivetted centre plate, solved the chatter problem and significantly strengthened the clutch.
Parts were only somewhat interchangeable, but only in certain combinations.
An extra plate (as in the aftermarket variety) is of dubious benefit in any of these designs. Stronger springs are a benefit, but have the downside of putting even more pressure on the weakest link in the chain, i.e. the clutch pressure plate.