well I guess Driveline 101 explains PHASING of the u joints---
I agree with 34 40 about lowering the shock tops just a wee bit so the weight won't hang on the shoch when truck jacked up off ground
The shock mounting angle really just effects the dampening rates a bit because of the angle ---one of the main oem reasons to angle them is for clearance during full suspension travel and /or clearance for the exhaust over the axle. Once you have them mounted in regards to there travel length, I would suggest fabbibg a mock up tube at the shock ride height length so the truck chassis sets at that level while you do the drive line angle work---the spring perches don't look like they are welded to the axle housing tubes yet??? that is good as you can tip the housing for the u joint angle before you tack them-----