Update: I removed the entire cig lighter assembly, leaving a hole for me to mount the cutout switch, but the hole is bigger than switch. I couldn't find a plastic adapter, fortunately I tried "power brake check grommet and it fit perfectly and the switch is secure. Here's the pic of grommet...
Here's the ash tray switch..
I will post more pix of install and unit later tonight. I will also be running the wiring through the firewall grommet into the bay and wrap it up secure, so it will be ready once they weld the cutouts.