Generally, to at least get you in the ballpark and driving:
With the Tahoe at ride height, adjust the bars so the axle is centered or slightly forward in the fender wells. All four should be the same length (bottom two at X" and top two at X"- top and bottom obviously won't be the same lengths).
Measure the angle of the front yoke on the driveshaft and make the rear yoke the same angle. Manufacturer specs may call for 1/2 a degree or so less (rear yoke/pinion pointed down) than the front angle. You can adjust the top or bottom bars or a combination of both to roll the rear end the direction needed to set the proper pinion. Magnetic angle finders are cheap at Harbor Freight.