Okay, lets break it down Barney style for you. If you add 3" longer than stock shackles, the rear comes up 1.5" because when you put 3 extra inches on one side of a leaf spring and leave the other end in the same place, (go ahead, do the geometry on your fingers and toes. I'll wait.), whatever you lifted at one end is gonna lift the axle in the middle by half that. Use whatever length shackle you want, the rear only goes up about half of the extra length.

Stock from the showroom floor, an H3 would be roughly 22-22.5" from wheel center to front fender lip and the rear would be about 24.5". Now lifting the front 1-1.5" with the torsion bars gets you close to level and in the suspension sweet spot. BUT, mechanically it could go as high as about 24.5" which goes from level to about 1-1.5" off from a lifted rear.

 

Plus most aftermarket 3" shackles are more like 2.5" difference from hole to hole from the OEM so the "true" gain will only be 1.25".

rsc, breaking it down "barney style". That's some funny stuff right there.

 

That's right RSC, simple math!

Did you have to go barney style on that explanation? lol