Maldol and Diamond are the mounts of choice in the Ham Radio Community....tlflow's mount is a very strong type that should suit you just fine....
The major problem with any type of "lip" mount is the high probability of the mounting screws biting through the paint and into the steel....thus causing a rusting issue....I know of no other way to securely hold the mount without that problem....therefore that is not an option for me.
On my last runner, a 3rd gen, I drilled a hole for a Motorola mount for a 17" 1/4 wave 2 meter antenna...that worked well for 3 years and it rusted around the mount....that was chore to clean up and repair....glad I caught it early to fix it....
I now use a 2 meter/440 Mhz halo magnet mount that works very well....however, your CB antenna is much to larger unless you opt for a larger 3 magnet system....not great....
Think I would try a mount, maybe the motorized version for garage use, mount it on the roof rack and run the coax like Antman did...that was cool....
For my radio install, I used a remote head unit, mounted the main unit in the hole where the non-exhistent JBL speaker goes and the head sits on a mount fabricated in the vacant space below the 12v outlet....looks like a factor install up front....need to dress up the wires in the back to make it look clean.
Let me know if you want pics and I'll be glad to post.