I mean the included angle. The rear axle should be 2 degrees down from the angle of the rear part of the driveshaft.
Under thrust, if you have the driveline in phase, the rear will rotate up slightly and take it out of phase. You really can't get it in phase with a centre bearing 2 piece DS anyway because the centre bearing is fixed to the floor.
With a 2-piece DS, it isn't that important but, you'll want to set it up like I am suggesting.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto tune, 100 shot on BBR tune, best et: 11.38 at 120.85
2012 GT, Candy Red, Brembo, 3.73, Tech, Comfort, etc. Procal tune, Roush upper, UMI LCAs, Steeda red bracket, GT500s, 28X10X16 Hoosier slicks, best et: 11.91 at 115.23 RIP