Thanks for the reply! What I am referring to is if you got rid of the stainless/aluminum mount you have your antenna mounted to and drilled a hole directly into the part that meets your tire to mount the antenna, would this give a sufficient ground? My tire mount is bolted directly to the tailgate and not the bumper. I figured any metal on metal surface that completes a circuit through the battery is a good ground, could be wrong.
try doing a continuity check to see how good the ground it. My antenna mount is right against the paint and I have a good ground. Where you would run into problems is if there were insulators that would prevent the antenna making a good ground. Try it and see where it goes. If you need to run a separate ground you can down to the frame and not have to drill into your painted panels.
R/
Will