1997 Suburban Torsion Bars

[SWEET7T]

CEDJUNIOR...
If the front wheels are off the ground, the suspension will droop all of the way, and there will not be any difference when the torsion rate is increased. This WILL make it easier to turn the bolt, but it isn't very hard to turn when it is on the ground.
Don't get me wrong on your idea of measuring from tire to wheelwell/fender to equal out the front suspension, but you need to be careful doing this because of a load on the vehicle, or the ground being uneven. They come from the factory being equal... Assuming that the Burb is still 'factory', an equal amount of turns will be sufficient to keep the torsions equal.

BOBFRAY...
I forgot to add, Turn the bolts like once or twice, then move your burb up and down the driveway a few feet. This will allow the suspension to 'settle'. Settle being the only word I can think of... But your tires will want to move inward slightly due to the fact of them going down. Don't worry, you wont be able to notice it, but on IFS, the tires move inward and outward and the suspension cycles up and down.
Also, good point made by CEDJUNIOR on your half-shaft angle. A little steeper angle wont be a problem, but some bogous steep shaft will wear out quickly.