I worked for years in the two-way radio business. I still believe the best way to do it is to go either through the firewall, or under the cab and make a hole , install a rubber grommet and seal it with black silicone RTV. Connect directly to the battery connectors.(yes both the + and -) It was difficult, but I went through the firewall and sealed the hole. If I remember correctly I found a rubber plug that I was able to perforate. Doing that eliminates a lot of potential for interference on the 12 volt line that serves other accessories. My radio was initially an Icom IC-7100 HF/VHF/UHF that is located behind the back seat with sheilded CAT-6 control cable and a 2 conductor speaker wire running to the front of the truck. That radio proved to be much too complicated to be operated while driving. It's been replaced by an Icom IC-706 MKIIG. I installed a stake pocket Stainless steel whip base, on the back driver's side, running the coaxial cable through a plugged hole behind the rear seat, and fishing it through the frame rail and up into the stake pocket. A body (frame) ground was also connected to the stake pocket whip mount. It works like a champ eith the Texas Bugcatcher HF antenna.