As mentioned above, I removed the single u-joint and installed a double u-joint and a Super Beetle bushing.
This is the double u-joint. I couldn't find a 16mm x 60 spline double u-joint so I bought a 5/8" by 36 splines double u-joint from kartek.com. It is made by Sweet Mfg. My old single u-joint clamped onto the shafts. The double one uses set screws.
The splined end of the u-joint wouldn't fit over the shaft on the rack so I used a 5/8" drill bit to remove the splines. If you look at the shaft on the rack you can see that it has flat spots at two different depths. It has a shallow one on the end, then a longer, deeper one, then a shallow one again.
I was a bit concerned that with no splines, it was only the set screw that prevented rotation of the u-joint in the shaft or movement of the u-joint along the shaft.
I made a little aluminum piece that I epoxied onto the deeper flat area in the shaft. It will help prevent u-joint rotation or movement along the shaft.
This is the Super Beetle bushing. It replaced the bearing previously used on Super Beetles. I am glad they replaced the bearing because I don't want any electrical connection between the shaft and tube. I hope the Nylatron bushing isn't conductive.
This is the bushing installed in the tube and the modified steering shaft. A 5/8" x 36 spline piece is welded in the end. The splined piece is an Empi part from mooreparts.com. If you get it from them on eBay shipping is free.
This is what the completed installation looks like.