Hey Carbon.. First off.. !!! Anyways, based off little knowledge of CarPCs, but decent knowledge of computers in general. I think you could do it. What you would need is a 3 (if they make it) or 4 port VGA splitter to output to those displays. You're also gonna want to have the same size monitors, because if you use a splitter, it uses 1 signal to output to each monitor. That signal needs to line up on each monitor.. Other than that, Umm.. Yeah, that should about do it..
One question we all want to know: Why would you put a monitor in the trunk?!