Dave,

More imprtant than height from ground is the angle. Get the chassis level, then get an angle finder, they sell for less than $10 at Harbor Freight or Sears and place it against the transmission output shaft. Ideal down angle is 3-5 degrees. Then measure the angle on the input shaft (pinion angle) of the differential center section. The angles should be similar but opposite. In other words, if the transmission shaft angle is 3 degrees down, the input shaft should be 3 degrees up. That will make them parallel. In live rear ends people will put some down angle in the pinion to allow for the rear end to twist up under torque. That is not an issue for you since yours will be solid mounted. The drive shaft angle should follow the guidelines mentioned by Jack.

hope that helps

Pat