In 1974, Chrysler transitioned C bodies to what is known as the "spool" mount system. This is where there is a round rubber insert molded into the actual steel mounting bracket. If the rubber should fail, the metal structure surrounds the bolt and will restrict the movement of the engine, so that under full power the engine doesn't lift up and destroy the fan shroud, linkage and other underhood areas. Unlike the earlier C-Body's, spool mounts use a specific K member for big blocks and small blocks. So, our factory reproduction brackets must be used with an oriiginal big block car. If you are putting a big block in a small block car, you must either swap the K member to a big block one, or use our special conversion mount brackets.