Why go to a CB shop if this is a cigar lighter, mag mount install?
^^ This x2. Any reputable radio will be fine out of the box if its just getting paired with a mag mount. Look for the best ANL and NB in the biz if its gotta take its power from a cigarette lighter socket. Not much point in going all out on the peaked radio to have that signal go nowhere through a significantly compromised antenna.
The antenna is really the most important piece. If he just won't go with anything other than a short mag mount then it doesn't hardly matter if its a $5 ebay radio that is 40 years old, the radio won't be the bottleneck in that system. On a truck it should be pretty easy to do a better antenna setup that can just be unscrewed when not needed, just have the coax run be the only semi-permanent part of the install. A full whip would be best, something with a 6-ish foot like a wilson 1000 might work pretty good.
I almost want to recommend the President Bill FCC radio. I mean, I do, but I am just as bummed as your friend will be that it does not have adjustable receive gain. The screen is also kinda small and hard to read, scan is slow, and the speaker is not very loud so kinda needs an external speaker or use an aux cord to pipe it into the car's audio system maybe. Those are it's downsides. On the upside, very small radio that can be mounted anywhere, President sells extra quick-release carriages for it so you can easily move it from vehicle to vehicle, very good ANL/NB + Hi-Cut, channel change buttons on the mic, automatic and manual squelch, NOAA weather capability, adjustable screen colors, simple/easy interface and buttons.
I am not as blown away by my President Bill FCC as I had hoped but it is a nice radio that lends well to swapping from car to car and has decent features, and is easy to use. Automatic squelch kinda makes up for the lack of adjustable RF gain. Still needs a good antenna, the best radio can't work miracles with a mediocre antenna.
Why would they include FM on a CB? I am old school.
FM Just became legal in the USA. Probably nobody is really going to use it much (my opinion) but we'll see. The President Bill FCC is rumored to have a straightforward internal mod that unlocks FM capability. Something you can look into.