I don't know if this may help, but my '84 K-5 Blazer had a longer tailshaft in it than my '78 Blazer had. When I lifted the '84 Blazer, I had a vibration just like you guys have been experiencing.
The local 4x4 shop tried some 3 degree shims and it helped only a little. We then tried some 6 degree shims and it was better but was still there. The shop had no other recomendations so I was on my own to cure the problem.
First I reallized that 6 degrees was keeping the driveline at the axle in perfect allignment, so it had to be the angle at the t-case.
I then shimmed my T-Case cross member down using some 1/2" bar stock that I had drilled holes into to match the holes in the cross member. I put longer bolts in and took it for a test drive and all of the vibration was gone. I then took out the 6 degree shims and put the 3 degree ones back in. Had no trouble after that with any vibration.
I had the same trouble with my '84 Toyota x-cab 4x4. It has the same type of center support bearing that we use on our Rams. I did the same shim work to the T-Case cross member like I did with the Blazer and lowered the center support bearing a 1/2" also to get rid of the vibration. A couple of years later it was time to replace the center support bearing and I was shocked that a new one was $166. I then eliminated the bearing by going with a 1-piece driveshaft.
I think the 1-piece driveshaft is the way to go.
If any of you go with the 1-piece driveshaft, make sure it's made with some thick wall tubing as our mighty engines will twist anything less like a pretzel.