Some questions:
if this a dedicated trail rig, or will this see road time? If it will drive on the road, you want to maintain your camber, so do a search for "cut and turn".
As for angle, that depends on the type of driveshaft. Are you going to use a stock shaft? Or one with a cv joint?
If a stock style shaft (standard ujoints on both ends) then the yokes of both the transfercase and the pinion should be parallel to each other.
If a cv joint, then the pinion should point straight towards the t-case.
If you plan on going to a cv joint, and you have a 727 tranny, you May have to grind a little off of the tranny for clearance, but I didn't need to.
For excellent reading on driveshaft angles, go here and go into the tech section (link at top of page):
Tom wood's custom drive shafts - Tom woods custom drive shafts custom driveshafts specialist
Angles are more critical if the rig is going to drive on the road. On the trail, not as much as you are spinning at low rpms. The more out of whack you are with your angles, the more vibrations you will feel as you go faster.
And don't forget extended brake lines!!
Hope this helps...