Pinion Angle

[chevyrestoguy]

I'm about ready to swap the old 3/4 rear end out of my '64 C-20 and replace it with a 12-bolt out of a '79 Suburban. I am planning on also installing 4" drop springs while I've got it apart. Because I'll have to weld in new perches to the 12-bolt, I have a question:
On coil spring set-ups with lowering coils, what is a good pinion angle for a street-driven truck that'll carry a load every once in awhile? I've done this before on leaf-spring cars, and it usually winds up about 2 degrees down, but I'm not sure if this same theory applies to a coil spring/ trailing arm suspension.