I have to ask, since I don't feel like reading all of that.
did you replace the U joints?
they can still be tight, but have a area worn, if they are old. now that you have changed the angle of the drive line they can be (jumping up over the worn area's) and causing a vib. I have lifed many high milage trucks and it only took a few before I started replacing the (tight) u joints for new ones and the problems went away. some of the u joints that (felt) good, when you took them apart (some) you could see and feel the old worn area's. some you could not. I tried some of the ones that you could not... and the bearing would eat them selves in oh... 500 to 2000 miles.

just a thought.