I wouldn't shoot for 6* unless you have actually measured the over all pinion angle. The 6* suggest on TRS should be considered a starting point, but every truck is different. The proper way to measure overall pinion angle is the difference between the driveshaft angle and the tail housing of the trans or Tcase should be the negative of the difference between the driveshaft angle and the pinion flange.
So lets say the tailhousing measures 78* and the driveshaft reads 75*. So that would be a 3" difference. Then the pinion flange reads 71*, so the difference is -4. Add up the two difference's to get an over all pinion angle 1*. You are typically shooting for o* overall pinion angle, but under 2 is "usually" acceptable. Sorry its hard to explain online.
Here is a quick pic I found online.