you could convert it to gauntlet, but i believe it'll be a little harder than just plugging up a gauntlet board. that looks like a proprietary harness, and i know guantlet also has a special harness.
you'll have to make a harness for the atari board. you could probably just use the existing harness and put in a edge connector that fits the gauntlet pcb.
from what i understand, it's possible to run gauntlet off a switching psu(which is what's in there), this helps. finding a working atari psu might be a bit difficult and expensive.
you might also be able to make some sort of gauntlet to jamma adaptor, and then jammatize the cabinet. then you could swap out jamma boards in there.
do a search on google groups. i'm sure there's a ton of info about this. you should be able to find pinouts for both games as well. here's a link:
[url http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&group=rec.games.video.arcade.collecting] rgvac[/url]