The only solution for the torsion bar adjustment is to read the guideline of GM.. The distance between the joint and the lower point of the lower arm is 122 mm +- 6mm as you can found on
http://elcova.com/groupee/forums/a/t.../841108936/p/1
The drawing is incorrect and I think that this is better ...
The other point to measure are only indicative.
As many people of the forum says, every H2 is different to another, but it the same on other car... 1/2 inch is not a problem... 1 or 2 is a lucky choice... depend if you make OR or only HGW... I have buy my H2 used and the owner before have lowered of about 3" (without give me notice) ... results... destroyed right front shocks...and replace pitman and idler arms..