If you have a 2008, do you have upfitter switches? Does your radio need constant power, or does it matter if it is switched? Some of the upfitter switches provide about 30A. That ought to be enough for a 2m transmitter, right?
There is a fuse box in the passenger side foot well. As far as where to put the transmitter body, I don't know exactly. Is it too far to put it behind the back seat?