Just an update. Got the wiring thru the firewall like everyone suggested. Just needed a coat hanger to shove thru the firewall. Nice, clean installation. Ran the power wire direct to the battery and have it tie wrapped along the main battery cable and thru the top post protector, can't even tell it is there. I ran the ground wire to a grounding post on the top of the firewall. Seems to be a good ground. Thanks for the help everyone.

 

It is not a bad idea to clean all the factory grounds where the ground straps attach, and look around the truck for more places to ground pieces.

The 'never sieze' made especially for stainless steel
has small particles of copper in it that improves ground connections
if a small smear of it is placed at the ground screw locations.

Those snap on ferrite chokes used liberally on electrical lines can improve radio reception remarkably.

Long time Dodge Ram guru Dave Fritz
who's day job is chief of IT for Virginia Tech
is a enthusiastic ham:

http://dodgeram.org/ki4cy/ramradio/radio_mt.htm

 

or a tooth washer.