This year my plan is to have a way to get on 80 meters while mobile so I purchased a screwdriver antenna made by Diamond. I picked this one due to cost compared to a Scorpion and that it mounted with a PL-259/SO-239 connection. With this mount I have more options available such as hamsticks, antennas with PL-259 connectors or I can use the mount for an external connection without running coax through the door of the truck. This is a Breedlove part number 910.
The installation on the 2015 Colorado requires that you unsnap the black trim along the top of the bed and cut out the section that covers the stake pocket. Then you need to plan your coax route down along the inner wall of the bed and how to get it into the cab. Mine came with the SO-239 mount but you can request the 3/8 x 24 or the NMO style mounts.
Below is the mount installed in my 2015 Colorado. It is a little tricky installing this mount as you must keep upward pressure while tightening the screws evenly.
What is not seen is the choke kit that is zip tied under the bed along the gas tank filler pipe. The choke kit is sold by KF7P. The product name is W1HIS Excellent choke kit. I have been using one of these for 2 years on my AH-4 tuner with great results. So this choke is sealed inside a piece of 2" PVC pipe with end caps. The coax exits the choke and enters the cab floor through a grommet.