I got rid of the double din cd player and got a single din one and mounted it under there. Better sound quality out of your speakers to, and if you get the right one and the cb has an aux out or something along those lines you can hook it into the speakers.
Depends, maybe if he has them both on 40 he will get 80 channels, lol, just kidding.
Depends what you use them for, the semi I drive for work has 2 in it, I usually have 1 on ch 40, in case there are any wide loads that I need to know about and the other on the "talk shit" channel, ch 3 which I can also be handy for hearing about traffic problems and speed cameras, etc.
I know this isn't a truck, but I guess some people need the same in their 4x4's, or want them...
Have a look at Hodges posts, has photos of instal above the gear stick boot under the ashtrays.
I copied it, looks neat and you should get two in side by side