I've been down this road listened to people tell me it was the engine it was a bad pressure plate...all I'm saying is check the external easy stuff first don't tell the guy that he needs the rotating assembly machine shop balanced as the first move...for years Ive seen it on here its always the most invasive expensive thing given as advice. I'm glad I know what I'm doing and can keep a car running... feel bad for those that ask here. OP do me a favor PLEASE come back here and tell us what it is/was... :lol:
to elaborate further how did I know it wasn't my engine? I pulled the 340 and dropped a 318 in and, THE SAME VIBRATION like said been down this road. Its a process of elimination and yes get the checkbook out...if money is an issue you'll get upset fast. I did however get real good at getting a 4 speed out in less than an hour :)