I have the same radio, the main unit fits under the driver seat in my 03. (no power seat setup which makes for enough room) The remote is mounted on the center flip down box so that I can operate it with my right hand while driving. I also have a home made bracket which allows it to the remote to fit in an open spot on the dash. It makes for a very nice smooth operation and you will like the FT-857 in spite of the complicated menu. For an antenna, I have a high sierra mounted to a tool box in the bed of the truck.
It makes for a nice traveling or camping set up but won's compare with my 70 ft tower and 7 el beam with 1500W linear amp.
K5IP