Finished
Finished this up last night. Ended up making a few other changes. Found a longer bolt with the correct thread pattern as the adapter from the kit. Threaded that into the adapter along with the screw base. Drilled out the center of the bolt head and threaded in the screw for the antenna. Drilled out a counter sink for the adapter to sit in, soldered everything up and finished it all up with some RTV to seal the ends. Painted it with some shadow paint and clear and mounted it.
Almost forgot to mention that I am still able to pick up HD radio without any issues!