SWR just won't come down.....

I suggest that you check out these websites for detailed information:
www.RightChannelRadios.com/pages/high-swr-troubleshooting-flowchart-pv-c0-91.html .
www.FireStik.com/tech-docs.htm has multiple sections especially "swr testing & setting" and "swr troubleshooting".
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Since you have changed coax cable and moved the antenna up and down with no effect, it is time to check the antenna ground plane. In simplest terms the antenna ground plane allows the antenna to preform as well as the antenna can perform. If the antenna ground plane is faulty, you will have an excessively high SWR. If attempts to tune the antenna has no effect, then the antenna ground plane could very well be insufficient.
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If you can get someone with a multimeter to check resistance on the lowest scale between 1. the antenna mount and the door, 2. the door and the door frame, 3. the door frame and the chassis; all should read zero.
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For example, if there is high resistance between the door and the door frame, you will need to run a short length of 10 or 12 gauge wire. This goes from the top bolt that connects the door to the top door hinge and the top bolt that connects the top door hinge to the door frame. Recheck the resistance between the door and door frame.
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Do not run a long piece of wire from the antenna mount or door directly to the chassis. This would bypass the door frame and also act as an antenna. For that reason, keep the lengths of wire short.
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While it may appear that you are grounding or shorting the door to the door frame, this is actually "bonding" the large metal components of the truck together to form a large antenna ground plane for RF or radio frequency purposes.

 

http://www.firestik.com/Catalog/NGP_3-Way.htm

 

It's very important the stinger is the correct length before starting to tune. (Every Wilson I've had, the stinger had to be shortened. The last one came with a 63" and I only needed about 50" according to the chart.) Be sure and check the "Wilson" site AB7IF linked to. Depending on how long the shaft below the coil is, will determine how long your stinger is. If you get this all as it is supposed to be, and your SWR is still high, I would run ground straps from the mirror mount to the door, from the door to the body, body to the frame. Flat braided ground straps are best, a piece of coax makes a suitable substitute. (solder center conductor to braided sheath and solder all connections.) If that doesn't help, I would stop by a CB shop, or find someone who has experience in adjusting SWR and have them lend a hand.

 

The basic antenna is a dipole, which is simply a section of wire that is 1/2 wavelength long that is cut into 2 sections that measure 1/4 wavelength each. One section of the wire is connected to the center of the coax, and the other side to the coax shield. The dipole works well when it is raised up high - the height depends on the wavelength. The dipole is usually oriented so that it is parallel to the ground, but can also be oriented vertically. Now imagine that you take the lower section of the vertical dipole and orient it so that it is 90 degrees to the upper vertical section ( that is, parallel to the ground). If you now remove the lower section, the remaining upper section becomes the common 1/4 wave vertical antenna.

But since the 1/4 wave vertical antenna is only half of the dipole, it still needs the other half to work. In a mobile installation, the metal of the car or truck becomes the missing lower half, and is referred to as the ground plane. The larger the metal surface, the better the antenna will work.

In a NGP system, the ground plane is in the coax itself, and is the reason that you have to use the coax that is specific to that antenna.

 

Consider this the post mortem on Cyclerider's misfortune. Here are the most important things I can tell you about CB radios.
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1. Never, never ever operate a CB radio unless it is connected to either a real cb radio antenna or a dummy load.
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2. Always, always, always check you SWR by using an external SWR meter immediately after radio installation and BEFORE you start using it.
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3 Never, never ever operate a cb radio if the SWR is 3.0 or higher because you can damage the finals (power transistors) in a fairly short time.
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Cyclerider, with your extremely high SWR you have a very serious problem. If you fail to get the high SWR corrected, any other radio will ultimately suffer the same fate. It is probably time to get some hands-on help for your setup. Either somebody who has gone through the same senario successfully or a competent [and I stress the word competent] radio tech.
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Sorry for your misfortune. I hope this can become a teachable moment for others to avoid what you went through.