Vibration in driveline or motor/tranny mount ?

Hey People -

I just picked up this 65 Dart 273/Auto, and it has a vibration in it. I thought it was a bad u-joint (ball & trunion), but I notice it vibrates somewhat when in park or neutral, although not nearly as much.
It does it when accelerating from a stop, and it's worst as you go from 25-35MPH. It makes the steering wheel vibrate, but the back of the car feels fine. When I played with it in Park or Neutral, and brought the throttle up very slowly, then back again, I feel a vibration in a specific part, but still, no clue yet.
I need to get under there and check out the ball & trunion (blooming onion?) and maybe jack up on the engine and tranny a bit and see if any of the mounts look bad.

Just curious if this is indicative of one or the other, because when I've had the u-joints go out in other cars before, it usually didn't produce a vibration sitting still in Park or Neutral.