I found this in a folder on the Mac, finally: Worked great for the 780 years ago.

"Driveline Take-Off Vibration: Shimming May Be Required. From Volvo Technical Service bulletin 45/102 Jan '91. [Symptom:] Take-off vibrations at low speed, especially with high acceleration and/or heavy load, can occur in some cases. [Solution:] The level of vibration can be reduced by changing the vertical position of the center support bearing. Best results differ from car to car. Start with a change of 6mm (1/4") upwards. If results are not acceptable, try positions from 5mm (3/16") downwards to 12mm (1/2") upwards from the original position. Note that clearance between drive shaft and fuel lines must be at least 20mm, and between drive shaft and the fuel tank at least 16mm. Shimming upwards should not exceed 12mm (1/2") and after re-positioning the center support bearing housing should not contact the floor pan."