[Phast SVX]

You have the smallcar trans mount correct? The driveshaft is most likely coming into contact with the bottom of the shifter place(black plate on the bottom) I had this problem for a while too it took me forever to figure out how to get rid of it without throwing the drvieshaft out of balance. but i did it....

out about 3/16" (or play with this number) worth of washers inbetween the transmission mount and the screw holes of the mount. This will drop the trans down a little, and shoudl be enough of a drop to keep the driveshaft from tapping. If its only hapening in first gear, then its barely hitting.,....the amount of drivetrain slop in first is the higherst, that with the angle of the bottom of the shifter when in the first position. IF you need a picture, or want a better description do a search on my name or i can find you the picture when i go home on friday
phil