I have a tunable 4' Firestik on my mirror right now but would rather have it on the back bumper like I had one on my Tacoma. Good coax cable is sold in 3' 9' and 18' lengths, something to do about the signal works best with 9' multiples. (Dont ask, that's all I know about it lol) I have my Cobra 29 classic SWR mounted over my right foot and just 3' of coax going up behind the dash and out the wing glass. For a bumper mount I would drill a hole in the firewall, install a grommet and run the coax through and under the truck to the back. You want at least 2/3 of the antenna unblocked by metal body panels for best transmit/receive which is why on the back bumper worked good on the Tacoma since the tailgate is so short but on these Chevys you might need a 5' antenna. Just another reason I went with the mirror mount so it would be up high, but at the same time it can be a headache hitting on every tree limb on the trail or low clearance sign at a drive thru.