Most of the time when I've run into clutch chatter it is the motor mounts. If two short pieces of chain and two turnbuckles hooked high on the engine and to the frame, one on each side, stops the chatter it is the mounts. Flathead Fords up through 1948 had anti chatter rods from the engine to the frame which if left unhooked would chatter enough to shake things loose inside the car. Some genius decided to mount the engine at the very front of the engine and very back of the transmission which is still done by some hot rod builders---a real no-no.
to the frame stops the chatter
