CB Ground

If your running a ground wire from the antenna, i'm assuming you mean from the antenna bracket, and not the antenna itself...Needs to go to frame...NOT the negative side of the battery...Battery hook-ups are for electrical connections...

would also be better to use flat ground braid, and not round electrical wire for the ground.

 

You can also hook up the ground under the dash by the pedals somewhere away from the elements.

 

Multiple short braided ground wires.
Bracket to hinge
Hinge to body
Body to frame

 

The body of the truck is made out of steel. With a 72 inch piece of wire you're going to have some nasty common mode current because that wire is going to turn into a radiator. If a magnet sticks to your door then the door is made out of steel. I know the Freightliner Cascadia is that I drive are all made out of steel. The only fiberglass is the roof of the truck and the hood of the truck.

 

You did say you're driving a Freightliner Cascadia right? The largest metal mass will always be the body if the body is made out of metal which every Cascadia I've ever seen has been made out of steel.