I had a Cobra CB radio in my 82 245 diesel for several years (figure if I'm slow with the truckers, might as well talk to them). I mounted the radio under the dash of the passengers side, all the way to the left, with the factory mount. Tapped into power from the fusebox by passing wire through the back of the instrument cluster to the drivers side. Antenna wire was hidden at the trim seam all the way back to the rear right window, where I installed a through-the-glass "Cell Phone" type antenna. Worked out pretty well, looked great, but eventually someone unscrewed and stole the antenna and never gave it back.

Biggest thing: you don't have to do much to get the wires "out of the way", and if they're not in the middle of the footwell, passengers usually don't notice them (till the truckers bark up).

Mike