what are your plans for this car? circuit or street? does your four link arms have adjustment for length? the common practice is to have the pinion angle parallel with the crankshaft this is best for uni wear ,but for a circuit car we point the pinion angle down to use the "straightening under torque characteristic" of the drive line to make the car "squat" in power down out of corners to increase drive, in the 'AUSSIE LEDGENDS" cars we would point the diff down till it would vibrate then come back a bit because the more angle we could run the better it hooked up. But every car is different and you have to find what yours likes>