[Richard]

Stock the wheel is centered at the top of the arch. Some do not like that and move the wheel about 1" back which will center it more at the bottom opening. Rear of opening angles back more at rear. On high arch springs the axle can move front to back a lot. I get about 3" front to back with my Deaver springs from full droop to full bump, probably more with the new packs I had made. Just want to make sure wheels do not hit at full bump. A bit of work to determine that, requires disassembly of pack. You can see what I did in my thread.
The rear pinion should be set at the same angle but opposite as the t-case. If t-case 5 degrees down you want pinion 4-5 degrees up. Only exception is if running CV at t-case. Then you want pinion pointing directly at t-case, maybe 1 degree down from that.
No way to judge a spring pack by number of leafs. Do not have any idea where the OP springs came from. The Deaver springs I have for my truck are 10 leafs, They are really soft.
The stock 52" rear packs on my 72 had the pin centered.
One more add- the rear springs set an angle. If you just look at the picture with the higher springs you will see why axle is moved back. Many lift blocks move the lower pin forward for this reason.