I'd been driving my mini-van to work and back for several days with the setup quoted here with no interference problems. So I decided to move back into my truck.
I now have the computer back where it belongs on the back wall of the cab, powered up through the trucks wiring harness.
The monitor is back in the dash and connected to the computer via the VGA cable which is still under the carpet. The only thing different here is that I am powering the monitor from the cigarette lighter socket.
The Visteon is still under the seat and powered by the truck harness. A key change here is that I ran a wire to the ignition-in on the Visteon from a fuse on the truck instead of the 12V rail from the computer.
NONE of the audio is hooked up or powered on. I'm listening to the radio through headphones plugged directly into the Visteon.
Everthing was fine on my trip to work this morning. The computer (WITH the M2-ATX), the Visteon, and the monitor CAN all live happily together!
I'm, going to drive like this for a couple of days while I figure out what to hook up next.