There should not be any movement with the driveshaft installed in the car , no up or down and no side to side movement, EVER
It should rotate smoothly in a straight plane, no wobbling
Wobbling(up or down or side to side) makes vibrations, straight and true do not
It sounds to me that maybe the front U joint tranny yoke is junk
It should not move up or down or side to side when installed on the tranny output shaft
Get that good looking rascal up in the air on jack stands so you can run it in gear to find the cause