Use some RTV sealant on the coupling, it will help prevent leaks and will keep the collar from loosening. There should be no offset in the ball joint.
I've used the needle bearing U-joints, they are probably a service replacemnt part - they work fine as long as they have the proper lube level in the bell.
Put the truck on jackstands and run it up through the gears to the same RPM where you feel the vibration. Observe the front part of the driveline. If you can detect any flex or whip in the coupling area, that's where the vibes are coming from. I made a "splint" from angle iron and muffler clamps to stabilize this area, worked for a while, then got loose & fell off. At this point, I said enough is enough and dumped the whole POS for an open driveline. End of problems.
