Yea, 110km/hr is about 68mph, that sounds about the same as mine, in 4th and 5th gears. I found that after I have the driveshaft fitted with new u-joints/straightend/balanced, most of the vibration goes away. It still leaks though.
The thing is, the output shaft is in the way. If something goes wrong or the yolk doesn't fit you can't hone it. You can't really measure the ID either. So you're screwed and the whole thing has to come out.
I emailed NissanParts.cc to see if the bushing is still available. I can PM you about buying one for me if need be. Thanks.

Also, Peter's bushings don't seem to be showing up anywhere either. Darn.