In my K25 I have a Borgeson standard ratio box and the u-joint conversion. Everything works well, but I think I now also need to replace the inner tie rods (this short tie rod is only on a 4wD) to get rid of 100% of the play. I did not notice any change in steering wheel vibration after the u-joint conversion.
When you get the new steering shaft, make sure you understand how it adjusts at the steering box end. There is a set screw that is hidden under a rubber protective bellows, and it gives you quite a bit of adjustment in shaft length. At first I was confused and thought the rubber was just there to reduce vibration. You can loosen the screw and shorten the shaft length so it goes on the splines, and then pull it back out and tighten the screw so you get full engagement of the splines on both ends.
For those considering a similar conversion, make sure you understand the differences in the original GM steering box over the years. If you look at an article on the jeep shaft conversion you will see that early steering boxes have a different size shaft connection. However, since my new Borgeson box has the later shaft connection, I had to buy a universal joint shaft that was different than the one listed for my ‘75. If you have an early truck, I recommend giving them a call to verify the parts you need.