driveshaft angles

Just to be clear what my situation is. The car is on a 2 post lift that is adjusted so that the flat bottom of the rocker panels is flat (0 degrees). The back of the car is supported on tall jack stands under the rear housing tubes so that all the weight of the back of the car is on the springs. When in this position, the trans is also at 0 degrees and for reasons that are too involved to go into here it would be difficult to change. In this position the pinion angle is 3 degrees down. The driveshaft is 5 degrees down from the trans to the rear end. This means that overall the pinion is 3 degrees out of parallel with the trans. Therefore the angle between the trans and the driveshaft is 5 degrees down and at the pinion and driveshaft it is 8 degrees up.

After reading all these posts and looking at the diagrams and going to links to video explanations of how this should work, it seems that what should happen is to shim the pinion up 3 degrees so that the driveshaft angles are approximately 2 degrees up and 2 degrees down and the transmission shaft and the pinion are parallel. I throw this out there hoping to get some specific input on WHY this ISN'T what I want to do.

The only thing that I haven't been able to factor in is how much the pinion angle would change driving on a flat road at 60 mph. If it matters the leaf springs are new 6 leaf ESPO springs.

Unrelated to my situation, does anybody know what the angle of the original transmission is on one of these cars from the factory? I'm trying to figure out what people are saying regarding the pinion angle from the factory and how this translates to all the driveline angles from the factory.

Thanks for all the input