[Mikendebbie]

I had to google some of your terms to even figure out what you were talking about. Tar Heel antenna? Anyway - I went out and looked at the rear stake sleeves in my truck (my front sleeves still have the cap cover but I assume they are similar). Also googled "stake sleeves for Chevy" and you can buy them (who knew???) - I suppose they might be needed by (say) a body shop rebuilding a truck bed after a wreck. I have no idea if the bottom of the sleeve is open. I assume it is open for drainage. If it is open - you should be able to run the coax thru the sleeve bottom. My sketch may not be accurate - so use it at your own risk!

Edit: I looked again at my truck. The thing I drew as a "removable tie down" is actually a removable plug. The tie down loop is at a different location.

There is a CB/Ham sub-forum on iRV2 forum - a sister forum to this forum. You might find more info or post questions there.