I don't have CB experience, but here are some thoughts on Amateur/GMRS antenna mounts, in case it's helpful.
My last couple trucks I've drilled a hole in the center of the cab, and installed a Larsen NMO mount. I'll probably do the same for the new truck also. The downside is it's a commitment, and a bit of a pain, but it's a relatively straightforward process with a stepper drill bit and a magnet wand to get the shavings from out of the hole, which fall on the headliner. A ziploc bag rubber banded over the magnet wand makes it easier to get the metal shavings off the magnet. And once you have it done, it's good for the span of the truck. If you don't need it, or sell truck, you can put a rubber screwcap on the mount.
The upside is you get a much better groundplane, because the cab of the truck is the groundplane, so signal radiates "better". I'm not an RF expert here, but I've simply been convinced enough via various people in radio clubs that bedstake mounts or glassmounts have limitations. I tend to consider two radio scenarios, and two bands. You can use an amateur dual-band (144/440mhz) setup and radio, or you can use it with commercial VHF/UHF radios or GMRS. I've used that type Larsen mount with both types of radios (Amateur dual banders, and commercial part 90 VHF). That mount also lets you place a taller amateur VHF antenna when you need it, but primarily use shorter antennas to clear garage doors. The UHF frequency ranges are a bit different for Ham 70cm vs GMRS, so you can pick or swap those short antennas as needed, based on preference and judgement. Some links below for reference.
Larsen NMO magmounts are good too, and antennas can be interchanged the same ways, if the wavelength doesn't conflict with groundplane needs. I always have to look that up when I'm selecting the antenna, depending on the radio/band/project.
This RFMAX 3/4 inch Thru-Hole NMO Mount is optimized for vehicular roof mounting of an NMO type antenna. Typically used with VHF or UHF antennas, the RNMOT-58A-SUM-B-17I includes a 17 Ft. RG-58A/U (Stranded Copper Conductor) Cable & UHF Male (PL 259) Installed If this is not the NMO Mount you...
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Free Shipping - Comet Mobile VHF/UHF Vertical Antennas with qualifying orders of $99. Shop VHF/UHF Mobile Vertical Antennas at DX Engineering.
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This unit is a Black 'Phantom' style Omni-directional antenna with NMO-mobile mount operating at 450-470 MHz range. This antenna offers a powerful punch with up to 3 dBi of gain. Please note that this model REQUIRES mounting on metallic ground plane for best performance. The Phantom series...
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Single Rain Cap for NMO Mount. SAVE MONEY - BUY A 50 PACK. CLICK HERE.
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