'68 Barracuda 383 4spd - throw-out bearing/other issues?

with increasing noise in clutch took it in to shop for look at throw-out and other clutch components - got message that engine is shifting around when clutch is operated. Has not dropped trans yet - Will see mech. in a.m. and discuss - what the heck might be going on here? any comments welcome. thnx this is slant 6, 3spd to big block 4 spd conversion that has been doing fine for a while..