If you have any wires you need to run thru the firewall, including your CB cable you can drill a 1 and 1/4" hole thru the firewall where the factory drills it out for the snow plow prep option. Which is on the drivers side above the pedals. If you look you will see there is no insulation on either side of the firewall at this spot. Just get a drill or a right angle drill I believe works good from the engine side and get a hole saw the right diameter and drill it. The firewall is very thin (at this spot only I hope)
and you will drill thru in no time. Just be carefull dont go too far and catch any wires on the other side.
I cut the hole and ran my snow plow wires and a few other wires I have running out for switches and other stuff. I put a piece of sliced vacum hose around the edge of the hole to protect against chaffing and then put a small rag to fill in the rest of the hole to keep wind and fumes out of the cab. Then I just remove the rag to add more wires when I need. Not high tech I know but it works.
Also if you dont want to do that just CUT the coupling off the end of the cable and run the small diameter cable thru another grommet then get a new coupling at radio shack and solder a new one back on.
Or if you dont want to solder go to a CB shop in your area and have them solder it for you.
My .02 Diesel Dragon