i just redid mine last fall after installing the pocket kit got the rear axle centered on new pads let the car down off of the lift on blocks under the wheels so it was at ride height adjusted the pinion angle to match trans angle then tacked the pads took everything apart had cut down to 57" all good that's the way i've always done again leveling the rails was discussed on here sounded reasonable to me
I think that leveling the rails may have been used as reference point, then 3.5 degrees up, and 3.5 degrees down, which may stem from factory measurements (just guessing here).
But at the end of the day it is the engine/trans angle compared to the pinion angle that is what is the important thing. So as long as the rear is supported under the rear axle and the front wherever that is the relationship that will exist on the road.
I only found this out when checking mine. The guy that helped me, and who does it for a living also said that with leaf sprung rears the nose of the diff climbs under normal driving. He said that as long as the pinion angle is within 2 degrees (down) of the engine/trans angle then there won't be a problem.
I was just passing on the info as an option for 55forfun, because the 'iphone method' is a really easy way to check the angles.
Thank you everyone for the useful information! I have a digital finder. And I’m gonna be able to get away with not having to shim the rear axle or the transmission which is great all I did today was clean up the radiator and sand the core support really boring stuff so I didn’t take a picture so I’ll just add a couple pics and I got off work pretty late so just for everyone’s viewing pleasure I’ll add some pictures from work. (Taken over the mountains of West Virginia)