Rear Suspension Question..

The pinion angle should "straighten out" when leaving the line. That's why it's set nose down. The old Direct Connection book has the figure, I believe. I would think that the angle is dependent upon how stiff the springs are and, how heavy the car is.
Drilling the shocks to drain the oil is an ooooold "trick". I drilled a couple once and never used them. It became immediately obvious that they would be dangerous. As mentioned, they will have zero resistance and become ineffective. Thinking about newer shocks with nitrogen in them makes me think you could get hurt drilling them!
It's easy to over-do a Mopar suspension. A good rebuild of the front w/ a cheapie replacement shock and Super Stock springs (some apps don't even need a snubber) with a good drag shock in the rear are about all that's needed for a LOT of cars. I'm finding out that my 87 Mustang is much harder and more expensive to set up.