Driveshaft balancing...'71 with carrier bearing.

[MAC71Cheyenne]

Before I took this all a apart I marked all the yokes and shafts from the rear of the TH400 to dif. Two piece drive shaft.Replaced all the u joints and carrier bearing. Reassembled it all with aligning the marks but now have a vibration between 35 n 45 mph. Using a laser sight everything lines up straight, the one balance weight on the main shaft is there... Is there a way to check the shaft balance without tearing everything apart and sending it to a shop? I'm kind of leary about jacking it all up and running it up with a piece of chalk on a stick...
It is not a problem below or above those speeds.