For '67-'70, Ford revised the Mustang's clutch equalizer shaft to this design. From left to right is the six-cylinder, small-block, and big-block. There's a separate part number for 289 High Performance to clear the manifolds. The big-block gets a larger shaft diameter. The six-cylinder is longer, similar to the '65-'66. The 351W and 351C for '69-'70 got unique equalizer shafts not shown here.