Hi MTH,
I checked out all of your choices and think them solid. I say this knowing quite a bit about what I'm talking about. I hold a ham radio Extra class license, General Class commercial radio-telephony Federal License and Master Electronics Technician license in MA. Plus licensed to teach Electronics in MA. You can take what I say to the bank. I don't claim to be a no-it-all and as with anything, there are personal choices to make.
I'll start at the top of your list.
1. Any 40 channel AM only CB radio sold as is new and over the counter (not modified in any way) puts out the legal limit in terms of power which is 4 watts. This is covered under Eligibility in
this link. Some CBs claim higher power but if you read the fine print you will see they are referring to audio output not output at the antenna jack. Your choice will work as well as any other of higher price. Most of the higher price is smoke and mirrors.
2. Your coax cable will work fine with the Wilson antenna and it is the antenna I would choose if I didn't want the 1/4 wave whip that I have now. Follow
this link and under fiberglass antennas check out #5 that speaks about coax length. My understanding is that the firestick requires 18 feet of coax because it is necessary to match the impedance of the antenna at the feed point. On a firestick, the coax should not be trimmed from this length, rather the excess should be coiled up and stored in an inconspicuous place. I'm not sure if the same applies to the Wilson antenna. The Wilson antenna is a straight line antenna (not a coil type antenna like the firestick) and is, according the the Wilson web site a top loaded antenna. That should mean that the top loading makes up for the fact that it not quite 1/4 wave in length and should match the impedance of the coax at the feed point. Long story short, the length of the coax should not matter as much on the Wilson. I would still leave it at 18 feet just in case you may want to try out a firestick at some future date. My coax is 18 feet even though I am certain that it's length doesn't matter in my installation.
3. I currently have a 1/4 wave whip. It is 102 inches long and contacts all low flying objects and is a pain in parking garages so I have to tie it down when in the city and planning to park. The 1/4 wave whip is the best performing antenna for CB on a moving vehicle. Land stations may use a 5/8 wave antenna but that is not reasonable for a moving vehicle. Moving to shorter antennas from the 1/4 wave are all compromise antennas and the general rule of thumb is that the shorter the conductor of the antenna below 102 inches, the less effective it is. The Wilson, even though I could find no facts on gain on the Wilson site, should perform better than the firestick. I'm planning on getting one to test it out. I have a firestick and never use it.
4. The mount point is a matter of personal choice for the most part. The one that you have chosen will work well. For what is pictured, a bent piece of metal with some holes drilled in it and painted rather than stainless the price seems a little high. But absent an alternative at a lower price, it is acceptable.
The package price seems reasonable for all of the items that you have selected.
After you get the installation done you should bring it to a place that installs radios and have them check the SWR. They will know what to do. If you plan to do it yourself then here is some information. Antennas are a resonant device meaning that under ideal conditions, they operate at peak performance in the very center of the band and for CB that is approximately channel 20 give or take a small amount (the frequencies are not consistently spaced from 1 to 40).
SWR stands for Standing Wave Ratio and is the ratio of voltage maximums to voltage minimums along the length of the feed line. Pretty complicated huh? The ideal standing wave ratio is 1 to 1 meaning that the voltage is the same along the entire length of the feed-line. The best SWR in practice is considered to be 1.1 to 1. Standing waves occur in any medium in which sine waves may be traveling in opposite directions. This happens in oceans when the wind is traveling in the opposite direction from the water (tide). While swimming in the water there will be places that you will be moving up and down a lot (a place of maximum amplitude) and other places that you will see the water moving up and down but you are not moving up and down (a place of minimum amplitude). Maybe you have experienced this in a boat? In an antenna circuit any place where there is an impedance mismatch is a place where signal sent down the line is reflected back at the source. The most typical place where this occurs is at the place where the antenna connects to the feed line. The feed line is built to have an impedance of 50 ohms. All antennas that connect to transmitters in the US (for the most part) are built with a 50 ohm output and a 50 ohm impedance coax is connected to it and a 50 ohm antenna is connected at the other end. And when that happens, all is good and the SWR is 1.1 to 1. The antenna sometimes has to be trimmed to create this balance on channel 20. So, the swr meter is placed in the line at the transmitter. The transmitter is keyed (transmit button on microphone is pressed) and the SWR is measured on channel 20. If it measures approximately 1.1 to 1, you are done. If it is not 1.1 to 1 then it needs to be determined if the antenna needs to be shortened or lengthened. It the antenna has an easy method of adjusting this you just use trial and error to correct its length.
The reason this has to be checked is that if there is too much signal being reflected back at the source (high SWR), heat will build up in the final amplifier of the transmitter and eventually the circuit will fail and in today's market that will mean replacing the transmitter because that will be cheaper than having it serviced to replace the broken part.
