Thanks Chris for the comments. Yea, I was following the whole saga when your 2015 got totaled. She was definitely a good looking truck.
My plan was to mount the 4' Firestik antenna with the heavy duty spring and quick disconnect centered on my front bed lip behind the cab. I have a GatorTrax retractable tonneau cover, so the stack pockets are out. I was on RightChannel Radios today and I'm starting to rethink my idea. They have a Firestik dome mount, I'm thinking of mounting that on the front non-retracting part of my tonneau and going with the Firestik 4' Firefly antenna, seeing how the aluminum tonneau cover isn't as strong as my bed lip. May just my stick with my original plan, seeing how its ordered already. As far as that filler piece to cover the area behind the CB, I purchased an external speaker to mount on top of the plexglass / lexan, seeing how the CB speaker will be under the plexiglass / lexan and there is adequate space behind the CB to mount it along with the Mike mount.
I would love to run a Scanner underneath the CB, as you did. When I retired from the Fire Service, they were going to digital radios and going away from the analog radios that were able to be picked up on the older scanners. I remember I had a Realistic home scanner to follow police and fire when I was much younger. I'm sure there are digital scanners out there, but probably way out of my price range. Anyway, when I get the project all completed, I'll post some pics of the finished project.
Good luck with outfitting the 2018.