welding spring perches on axle

Is it possible to weld spring perches on axle and getting the correct angle without the axle being in the car?. Say the axle is sitting on a set of axle stands ..Can you put an angle finder on the pinion and go from there ??

Yes it can be done. The main thing you want to be sure of is that you account for any spring angle AS WELL AS the pinion angle. YOu cannot assume they sit flat when mounted.

Someone must have come across the "stock" specs" for perches...

Perches level on bottom, pinion 5* up is stock IIRC.

Is that where they belong on your car...

Stock is stock, but when modified every combination is different. I strongly recommend that you mock up the rear end in the car; you can just snug the U-bolts, put weight on the rear using stands at the same height as tires and use a floor jack at the front of the rear to adjust the angle, then tack or mark the perches in place. Pull the rear and bring it to someone with a BF welder to finish it (I brought our Dana to a metal-works shop all prepped and they welded it for free).