Bad Drive Line Vibration

Supershafts,
Yea I got a little carried away with that test. Thank goodness I have a spare indicator. I ran that test with no tires or drums and I did fell a small amount of vibration. The fronts are skinnys so I had my drag radials re balanced today before I did any road test. In one test I did run my new tires and wheels from my Dart and it was smooth until 5000. That's when I pulled the shaft and had it balanced a second time. I may be confusing the issue in my communication. I have read that SS springs rise 5 degrees under load so I have positioned the diff at 2.5 degrees down measured on the yoke with the drive shaft removed. The tranny is 2 down measured on the end of the output shaft. I removed the seal so I could get a good measurement. Does this setup sound correct before I run it?
Thanks for hanging in there with me.