Update, I bought a new antenna and a spring. (Here: https://www.amazon.com/gp/product/B000X3EP7I/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 and here :https://www.amazon.com/gp/product/B00042LC9M/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1) I think everything should just screw together now. I also bought an external speaker, any suggestions for the best spot to put that?
I have mounted in My XJ is a Galaxy DX-55V (Upgrading to a Bearcat 980 soon)
If your on the Cheap and need a good quality radio I recommend the Uniden BearCat 680 Or if on the really cheap the BearCat compact If willing to put out the extra cash for the radio I reccomend the Bearcat 880
I highly reccomend Uniden I have purchased many radios from them and have never had a DOA or any issues with Warrenty or CS
I run my CB with a 102" Whip on a ball mount. On your JK you Would be good Is the Rear Mount With a Firestik Fiberglass whip.
As to the Radio Mounting loaction That is up to you. Mine is mounted Above my head in my XJ What may Help with the mounting is that with the Bearcat 880 And 980 you can have a wireless mic for it.