I know I'll catch some woe for this, but here's my take.
All CB radios have exactly the same power output, which I recall as being 4 watts. This is by federal law and there is no legal way to increase the output.
The way to optimize (not increase) your transmitting range is to invest 20 bucks in an SWR meter.
SWR stands for Standing Wave Ratio.
The standing wave is the radio energy (the wave) that bounces back and forth in the wire between the radio and the antenna, a certain amount of this in inevitable (nothing is 100% perfect).
The ratio is how much radio energy bounces, as opposed to how much goes out the antenna, and a meter lets you adjust this to the lowest value possible. The meter simply hooks in (with a short jumper wire) between the radio and the antenna, and the adjustment is made by lengthening or shortening the antenna, which has a set screw for this purpose.
As for mounting the antenna, what antennas want is a "ground plane," which translates into mounting it dead center on the truck roof. This is an ideal state and if you do this, then even a $30 radio will get through where others can't.
But roof-center mounting usually is not practical, so what everybody does is mount the antenna to the driver's side mirror, or in that area, and it works fine. Remember we're not trying to transmit to Sweden, things don't have to be ideal.
But I think it's worth considering that your transmitting range is less dependent on adjusments, and more dependent on other things, mainly on how much radio traffic there is besides you. And that's a lot.
For the receiver (the other guy, not you), at some point your signal just disappears into the background noise, overpowered by closer signals. And there's so much traffic on the CB band that if you can transmit down the highway as far as you can see, that's a miracle right there.
Personally, I've always run $30 radios from Wallymart, and they seem just fine to me.
Another note is that CB ain't what it used to be. I'd caution that a lot of our peers seem to be lonely, grouchy people, and they love to vent thier frustrations in public. You'll hear more crappola on the CB than you ever dreamed could exist. Hence the expression "running quiet," which means I couldn't stand it any more and turned the damned thing off.
-a-