It's possible you have the wrong engine mounts...there were 2 different kinds back then. One was "short and wide", the other was "tall and narrow". Dunno how else to describe them, but the tall ones were thicker. Perhaps you have the tall and wide ones and that's causing your problem. My '68 uses the stubby short and narrow--you can compare them and tell the difference right away. Hope this helps and good luck! Glad another '68 is on the way back to life.