When my 330 2+2 was up on the rack the mechanic showed me where metal had been added to the driveshaft by a previous owner to balance it and cure vibration. You could check into this - I think it's a common problem and common solution. I've done extended cruising at 80 with no vibration at all. I'm happy with my 330 as well. It was a good solid car to begin with, needing some work. I've spent some time and $ on it but am still well within the very reasonable range to own a vintage V12.