The antenna is now mounted upside down inside the fender. I removed the antenna, removed the piece of wiper cowl that’s around the antenna. Unbolted the antenna mount. Slipped the antenna down inside the fender. Reattached the it to the mount and resecured the mount upside down. I then reinstalled the piece of wiper cowl.
Inside the truck bed there are rubber plugs at the rear stake pockets. I used one of those plugs to fill the hole in the cowl that the antenna used to go through.
I did lose some reception but not much. I typically listen the local radio stations and the signal is pretty strong so it hasn’t bothered me yet.
Having the antenna gone from its location will be nice in the winter when I have to clear snow off the windshield.