What is the right Z Bar?

Check the motor and tranny mounts, something may be moving around.

How long is the clutch fork?
Did you use a 12" or 10.5".
12" is correct for a small block "A" body.
You can check this by removing the boot on the side of the bellhousing.

Also there are different clutch fork pivot brackets for "A" and "B & E" bodies.

A call to Wayne at Brewer's may help after you verify that the correct parts are on the car.

Good luck