I meant whatever angle the trans was pointing down, the same angle pointing up at the rear or 1/2 degree lower to help compensate for torque kick up. Those HZ readings on the tsb I posted per rpm and speed were based on vehicles with a 3:55-3:73 ish gear ratio.
I helped someone on here years ago with a driveline vibration and it was caused by too much backlash variance in the ring and pinion. Usually over .004 to .005 variance will cause a driveline vibration. The only way to check is measuring backlash about every 3rd or 4th tooth around one revolution.
A small engine repair shop would have the sirometer I talked about, it's used to tune 1 cylinder engines. Too bad you couldn't borrow one for your dyno time to measure the frequency to find the rpm of what's vibrating. The 65-110 mph would be referred to the point of resonance for the vibration. Just adding weight to the driveshaft like a couple hose clamps could change the point of resonance to the point where you won't feel it. Have them opposing each other at the back end of the shaft. This is if everything else like angles are correct.
http://www.treysit.com/16.html
On the drive shaft I would say an 1/8" total is acceptable?