There are two driveshaft angle conditions that you have to be aware of. The first is the angle between the driveshaft and the crankshaft /rear end pinion shaft centerlines. This is the angle that causes the U-joints to articulate. The greater this angle is, the more the U-joints move and the more power is sucked up by the driveshaft/U-joints. Typically, the maximum design angle is around 5 degrees. At 10 degrees, you are going to have lots of power loss and noticeably shorter U-joint life(ask your buddy about his lifted 4x4).
The second issue is that the crankshaft centerline and rear end pinion centerline angles have to be parallel. This is because a driveshaft speeds up and slows down twice each revolution due to the U-joints. If the angles are parallel, the U-joints are in phase and the speed up/slow down of each U-joint cancels the other so there is no drivetrain vibration.
When a driveshaft is used as a stationary jack shaft like on the Halftrack, the crank/pinion angles will be the same, but they will be slightly offset so that the U-joints will move alittle and then the U-joint needles won't wear in one spot only.
I have not checked the angles and my halftrack, but I believe the flanges should be parallel. The only time the pinion angle is different from the crank is on a drag race car. The snout of the rear end is usually pointed down about 3 degrees. This is because the power level of the car and the suspension geometry causes the snout of the pinion to rise when under power going down the track. Sorry about the long explanation for a short question.