This is a good example of why you can't follow the Mopar Chassis manual to set pinion angle. It is just a re-print of a shop manual where all specs of a particular drivetrain combination are known.

Don't worry about if the driveshaft slopes up or down relative to the ground. Make the pinion parallel to the transmission as a base-line, then roll the pinion downward 2 degrees and weld your perches.