A CB in a 2011 G55? Barf. Go ham buddy, it's not that hard and you have many more radio options with remote heads that can fit in the compartment between you front seats. If you get into a new HF ham unit such as the Yeasu 857D, it can be made to operate on all channels, including FRS and the dreaded CB channels, alon with UHF/VHF and HF. A true all in one radio. As far as tires go, you I don't know much about converting a G55 to be more off road friendly, but there is a lot of info on pointedthree.com.
Also, if you are interested in antenna mounts that are inspired by the military versions, drop me a line. I have front and rear mounts available.
-J