The stock angle is 3 degrees
Check you engine/driveline angle by first getting your car level, referenced off the rocker panels. Check both rockers to make sure you don't have a "frame twist". If your engine/driveline angle is at or less than 4 degrees, and this is the combination you are going to stay with, then go ahead and match the perches to this angle. If you think you might change later, my suggestion would be to weld the perches at the 3* stock angle.
If the engine/driveline angle is greater than 4 degrees, I'd suggest correcting this first.
From my experience, car drivelines start to get vibrations above 4 degrees. I've also had vibrations start when the difference in the two angles reaches between 1/4 and 1/2 degree. Your experience may differ. I've had very good results staying between 3 and 4 degrees, and matching the angles to less than 1/4 degree difference. I use a jeweled movement inclinometer (for building model airplanes). It is very accurate, and was cheaper than the professional tools. The down side is you have to be careful not to damage it.
HTH,
Scott