Bill Upham at Mansfield Mustang has reproduced the ’71-’73 Mustang upper clutch return spring, which is PN D1ZZ-7523-A. This spring is correct for your Boss 351 as well. You can contact Bill via email ...
No-slip clutch/brakes keep loads and drives synced up. Machines that move loads to specified positions and hold them within a few thousandths of an inch need highly controllable, precision brakes.