If the pinion is angled up at the same angle as the rear of the transmission, then they will be parallel (and on the same plane.) Both the engine and pinion shaft also need to be parallel to the centerline of the truck (and thus parallel to each other.) The driveshaft would need to have the same angle on both ends and should work OK as long as the total angle (considering both horizontal and vertical angles). Here's a pic stolen from
DrivelinesNW. The driveshaft would look like the picture both from the top and the side.
