Clamp two hose clamps on the driveshaft with the bodies 180 degrees away from each other.
Start the car and run it up to 30-40 mph. Touch the spinning driveshaft with a piece of chalk taped to the end of a broomstick handle.
Stop the engine and examine chalk mark.
The chalk mark would indicate the "heaviest" side of the driveshaft. Rotate the two hose clamps bodies towards each other to counter balance the "heavy side" of the driveshaft.
Repeat the chalk test/hose clamps rotation until the chalk makes a circle on the driveshaft.
Apply weights or just leave on the hose clamps.