Rear Axle - Shock Perch - Correct Angle Question

Hey guys, the 74 CJ5 I'm working on was lifted and has 33 inch tires on it. I bought it this way. Not sure what the total lift is but I know the bolt centerline to centerline distance on the front axle shackles is like 6 3/4". I'm guessing this has about a 3 1/2" lift not knowing what the original shackle centerline the centerline bolt distance was.
The guy before me welded the rear spring perches with a new angle. The rear axle is now pointed at an upward angle, basically in-line / parallel to the output shaft of the transmission. He said he had some vibration with this set up, and from what I read, I believe this is an incorrect angle. For the perch angle to remain the same, I think I need a 3rd U-joint on the drive shaft. Or perhaps a longer axle if necessary and then welded some new perches so the rear axle is straight. Any advice would be appreciated and thanks!