I'm wanting to put in an original AMC CB AM/FM stereo, but also have my Alpine for CD/iPod playability...maybe there is some sort of splitter that could take the CB signal and patch it into the Alpine. I know I have RCA (Red/White) plug ins on the back of my headunit. The CB would still need power. I'm guessing the CB antenna is separate from the FM/AM antenna?
From what I've done in the past, you should go with a separate ant. I used to run the shorter, loaded 'Trucker' ant for my CB. Just have one - The car isn't wide enough to run both, and the 2 Ant's will interfere with each other's 'Near Field'. Good place is right in the middle of the back bumper - or on the rack (if not a magnet ant, or K-40). a spring on the ant will keep it from getting broken and interferring with the hatch.
Somewhere central on the car, and closer to the back, I'd say. See, the ant's near field will get pulled across the car, and if it's in the center rear of the car, the near field will get pulled across the roof, and you're best reception will be whatever direction you're pointing in, and gives it more intensity. if you put the ant somewhere on the side, the near field gets pulled diagonally across the car, and then you can get decent to choppy reception. Not the best placement.
some kind of Aux input/outputs is the best way to go to have the CB sound coming thru the alpine. Easier and neater, I found.
I'd keep the power separate - But that's my opinion.