In my '72, I have been chasing a drive line vibration at cruising speed (around 2700 rpm). I grabbed the transmission crossmember and found that I could twist it. The crossmember rubber insulators look like they're shot (that's where the movement was). I have new ones on order from Inline Tube along with the hold-down brackets. I will get a new transmission mount just to be sure. With any luck, this will solve the problem. We'll see. My fingers are crossed.
Interesting. I should check this on my car. I welded new ends onto my cross member when I reinstalled it years ago but maybe something got messed up over time. I have an annoying vibration at about 2K rpm then again a little higher rpm cruising speed of 65-70 mph. Could be old two piece rubber sleeved drive shaft out of balance or maybe the cross member bolts loosened up or weld broke loose.
With any luck, it's not rotted out. It seemed like the whole thing was twisting and the rubber insulators were moving too. We'll see. I'll let you know when I find out.
