The angles you described are ideal if they hold for normal driving/cruise and they improve/reduce the running angle as the trans and the pinion under load because both angles are reduced. The joint is strongest when the driveshaft is at the same angle as the pinion (i.e., zero angle difference between them. I use hellwig traction springs for a different application. They clamp to the front and are curved to resist the axle rotation much better than extra leafs and are adjustable and much cheaper than caltracs. They also stiffen the ride a bit. I don't know if they make them for this but they could probably be adapted.