Driveshaft vibes...
A used 93 Mk.8 driveshaft will run you anywhere from $100 to $200, depending on where you go.
Are you sure that it is your driveshaft giving you the vibrations?
I was experiencing a vibration in the 75 to 80 mph range, and I was convinced that it was my driveshaft. I did four things all at the same time, that eliminated the vibration.
1. Re-balanced all four wheels
2. Indexed the front wheels, so that the valve stem lines up with the yellow stud.
3. Replaced the OEM locking lug nuts with regular style ones.
(Note: These will affect wheel balance)
4. Replaced my strut rod bushings.
Hope this helps.....................