Correct way to set rear angle?

"driveshaft angle" is misunderstood. It really should be called "output shaft angle" which is the same as crank centerline. if the crank is tail down 6 and the diff is nose up 6, you are at 0: with the tendency for the diff nose to rise up under torque, you want it to be down in its natural state and the angle is dependent on the type of rear suspension you are using so when you are on it, the difference approaches 0 again. Lay rear in unwelded saddles and exagerated nose down state. cinch snug the U bolts. Get car back to road height and sit in it. have mate jack up nose with floor jack to desired level (it will rotate in saddles) let say -4 in relation to crank (output shaft) angle. scribe marks on saddles and tubes or tack weld, then remove and finish saddle weld beads. I found the crank line usually is down a few degrees so the nose is just shy of being level. A zero deflection at cruise is not recommended either as it wears out the U-joints as there is no load across the stationary roller bearings.