I did some tinkering on her today. I put it up on jack stands and leveled it under the front part of the box where the frame is flat. I then pulled the tires so the suspension was able to hand all the way down.
I took several measurements front left and right side to my 8 foot level on the floor. I found about a 1/2 frame discrepancy from side to side. I remembered that I bolted all of the cross members in and loosened up the two rear ones and adjusted the from with a jack. I was able to get it within 1/8 of an inch (until I haul something I guess).
I also made some adjustments to the shackle brackets because they didn't match by about a 1/4 inch. I was able to get them to match as well.
I pulled the leaf springs out since my 3 degree shims came in and measured them, one was about 1/8 taller when unloaded. I also found that the overload was installed backwards on one of the packs. I installed the taller pack on the drivers side. re torqued everything and measured again, pass side is 3/4 taller then the dr side, what the heck!
I figure that maybe the gas tank is on the dr side of the frame and 30 gallons of fuel is about 200lbs. I think I am going to get heavier springs anyways as these ones are better then the original but are pretty soft. I put in 1700 lb ones and I ordered 2500 ones, I will put the higher side on the drivers side to compensate for fuel and driver, lol.
I also installed the 3 degree shims. After torqueing everything down my pinion measured 1 degree nose up (originally measured about 5). I was able to put about 3/4" of shims under the tranny, which measure at 3 degrees tail down (was originally 5 down). Dive shaft is still about 4 degrees down from front to back. I was able to do a short road test and got it up to 70 mph for a few feet, I did not notice any vibrations this time
I will road test tomorrow since I have duty anyways.
Not sure the best angles for this stuff as the info on the internet is all about racing, but I gather leaf springs need a little more angle to compensate for all the movement the rear end makes up and down plus torqueing.
I also found some original advertising from 1981, pretty cool as I have never seen most of the options that they offered.