Because I was mounting the power box in the trunk, I ordered the Cobra AC702 extension cable and, for the extension speaker, a 6' Radio Shack patch cable (1/8" mini phone jack to 1/8" mini phone plug _ both mono). Neither cable would be needed if the box were mounted in the cockpit, but in my opinion both are essential for trunk mounting.   

Cost effective places to buy the radio include www.valcoelectronics.com and www.electronicsoutpost.com.  I’m currently using a small Radio Shack extension speaker (part #19-318A), which retailed for about $15 last time I checked. 

Because I wanted a stealth setup and didn't want to worry about a magnet mount scratching my paint, I bought the appropriate Jeff Anderson CB antenna splitter (email is jeffanderson@miata.net ), so I could use the factory antenna.  Jeff reports that the range is adequate when he drives sweep for 100+ car runs, and I've had good results with 40+ car runs.  I highly recommend Jeff's splitter because, unlike the magnet mount antennas many folks use, it doesn't risk my paint and doesn't force me to have a cable running out of my trunk or window. 

Tools I used for the installation were a Phillips screwdriver, a 10mm socket wrench with extension, wire crimp pliers, center punch and hammer, electric drill and 1/8" bit, wire fish tape and suitable beverages.  I had a helper to hand me tools and beverages, and to help with wire fishing, but she wasn't strictly necessary (at least for that purpose).  For later installations, I've also found it helpful to have some light twine or cord, to pull cables through the "tunnel" described below. 

Miscellaneous extra parts I used were an 18_22 gauge wire tap and about 3" of velcro tape.  Jeff's instructions for installing the splitter are excellent, so I won't repeat them here. I installed his "optional" switch to keep the antenna up with the radio on.  It allows me to put the antenna up, turn off the car, remove the key and continue to use the CB, and to play a CD while monitoring the CB. 

Once the splitter was installed, I fished the two extension cables through the "tunnel" between trunk and cockpit on the driver's side. There's a pre-drilled hole at the base of the seat belt tower, under the carpet edge. The corner of the carpet is attached with velcro, so it's easy to access if (unlike me) you don't have a roll bar installed. The roll bar makes it more difficult, but not impossible, to fish the cables.  It's easiest to fish a lightweight cord through the tunnel, then use it to pull cables from the cockpit toward the trunk.  To access the tunnel from the trunk, one needs to remove two 10mm bolts at the top and bottom of the plate between the trunk and the gas filler, and loosen a third bolt attaching the plate to the inside of the quarter panel. (With that bolt loosened, I could just turn the plate flat rather than removing it entirely.)  I temporarily left the pigtails dangling from under the carpet, as you'll see in the picture. (The "optional" switch is peeking out between the pigtails.)  After the pictures were taken, I pulled the excess wire back toward the trunk, so the pigtails are mostly covered by carpet.  Be careful about scraping insulation against the edge of the hole.

To keep gravity, etc., from pulling the pigtails back down into the cockpit, I used wire ties to snug the cables to the upper tab that holds the "plate" I mentioned above. I'd recommend padding the edge of the hole with electrical tape, a rubber grommet, or something, to reduce the chance of chafing through the insulation over time. 

Plugging the extension speaker cable into the box shuts off the handset speaker.  I wanted to be able to use the CB without the extension speaker, so the box needs to be where I can reach it.  As you'll see in the picture, I mounted it (using the supplied screws) near the center of the car, just in front of the trunk lid opening. As you'll also see, I left barely enough clearance to connect the cables. In later installations, I’ve drilled the holes about 1/2" lower, to provide more room.

For power, I tapped into the blue/red wire that powers the factory antenna motor.  This wire is not key switched, so leaving the radio on over night could drain the battery.  There is no key switched power in the trunk of my NB, so I'm taking a calculated risk. (Jeff Anderson disapproves.) The box grounds adequately through the mounting screws, so it is unnecessary to use the separate ground wire.  However, it can be connected to the grounding strap near the battery, as shown in the picture.  Re-usable wire ties work well hang the extension speaker from the wind blocker net. I haven’t found any convenient place to mount the handset in the cockpit, so I just leave it on the console, between my leg and the console, or in my lap. It seems to do fine, but I'm open to suggestions.

The pictures attached show "the box," the JA Splitter as installed (I used the velcro tape to stick it to the body _ it's visible in the picture to the left of the power antenna assembly), the ground attachment, the pigtails and optional switch, the mike and (larger than I currently use) extension speaker "between the seats," and another shot of the mike "ready to roll."

With this setup, the handset and speaker can easily be stowed in the trunk, leaving no visible evidence of their existence. On the road, there's no visible evidence we're radio equipped. We've achieved near_total stealth. The only permanent changes to the car are the two holes drilled to mount the box, plus the wire taps for the power connection and the "optional" switch. Total time required was an hour or two, taking it slow. 

There are other ways of doing all this, but this system works for me.

Some people have noticed that a separate "box" is often advertised as available for the WX 75 ST, and asked if they needed to buy one. One box comes with the radio, so you do not need to buy another unless you want to mount boxes in two cars at once, so you can move the handset between them.  

Meanwhile, happy zooming.
Don

My radio and external speaker.                                         Ground Wire.

Antenna splitter and spliced in switch wire.             My plugs on the driver side Radio and Speaker.

Radio on console                                                  Remote radio connector in the trunk