[Drivetrain] Not another driveshaft vibration

[navigator]

Hello Guys,
I have a 78 k20 4x4 all stock except for a NP203 with a part-time kit. I bought this truck recently. One owner, in nice shape. It picks up a strong vibration (driveshaft I think) at 55-60 on up. Thats it. nothing at lower speeds, or decel or shifting up or down gears. Tonight I replaced the U-Joints and both transfer case mounts. It was missing one mount bolt that I think happened from the vibration over time. The old U-joints seemed in so so shape. They were greased, all the needle bearings were there. I noticed a some chatter marks on the yoke side of all of them. Anyways the truck still has the vibration issue going on albeit slightly better.

I'm thinking I need to pull the shaft and have it checked for balance and straightness.

Am I on the right track or are there some quirks about this rig I may be missing. Thanks for any advice :-)

[USMCMP5811]

Have you had your tires ballanced?