I've built all of mine (that sounds like a lot, but probably half a dozen) between 1-4 degrees. Trans and pinion parallel and opposite, and between 1-4 degrees of angle between the flanges and the driveshaft. You need some angle to keep the lube moving in the u-joints, but more than 4 and you may get vibes. Even if you don't get vibes, you're asking more from the u-joints than needed.