Install the new driveshaft which will make setting the pinion angle easier to do since you'll have a better visual of the DS vs. pinion angles.
Just remember the pinion shaft is at the right angle if it points directly at the t-case output shaft/CV joint.
Should look like the first illustration below.
The next photos show how you can measure the angles. The angle finder at the rear of the axle housing shows a good way to measure the pinion angle which is exactly perpendicular to where the angle finder is measuring from. Flipping the angle finder as shown gives a direct pinion angle measurement.