If you want the best range, the fender is probably not a good spot for an antenna. Centered on the top of the roof is best, although IF you run a full-length whip (96-102"), the forward wall of the bed (behind the cab) can work well also. The biggest thing however is that the antenna be tuned properly (electrically resonant on the CB band). A SWR meter for checking your antenna is a wise investment if your radio does not have one built in.
Radio:
I would get one that has single-sideband mode (SSB). These radios are generally built better than AM-only models and will have better voice quality on AM because of that. Their main feature is the SSB mode though, which offers far greater transmission efficiency (on both the transmitting and receiving ends). The party you are communicating with must also have a SSB radio to use that mode however.
Some radios (black market) also have an FM mode. This mode tends to have the best clarity of all. Range is similar to that of AM. Again, the person you're talking with must have an FM-capable radio.
Microphone:
The quality of the mics that come stock with radios varies widely. In most cases however an aftermarket amplified mic (sometimes called a "Power Mic") will have much clearer audio, not simply because it's louder, but because they usually have a better quality pickup element in them (Astatic brand microphones are pretty consistent about having good sound quality). Avoid the temptation to buy "novelty" microphones such as echo mics and ones with built-in noisemakers. They tend to sound about the same as stock mics with the noise toys turned off, but the toys (even though they may sound cool) do make it harder for people to actually understand you (and are annoying to some).
With a full-length antenna and a good quality radio & mic, you should be able to reliably get about 10-20 miles locally (30-50 miles on SSB). On 27 MHz however, there is a phenomenon in the upper atmosphere that causes radio signals to be refracted (skipped) off of it back down to earth when ionized by the sun (check out the thread "
Shootin Skip"). During these conditions it's possible to talk hundreds, if not thousands of miles away. Depending on where you are and band conditions, it's not uncommon to hear far away places like Australia or Europe. It's a two-way path so being able to hear them means you should be able to talk to them as well, although if the band is very crowded, it could be tough at times to get a word in between everyone.
Anyway, hopefully that helps.
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