I've been researching antennas for my truck too, and I have pretty much settled on a fender mount like this one.

I've been thinking about two of these, actually, one for each side of the truck. One to run the 25W 2M/70cm? HAM Radio Antenna on, and one (on the other side) to run a CB Radio Antenna to. Both Antennas, plus power, can then be run through the firewall to the actual radio mount, which I am thinking of doing on the center of my dash/console using a bracket like this one.

The only other one I am considering is one that mounts behind the third brake light, but as you say, that makes for a mighty tall antenna.

-John