I haven't done a ton of research on this yet but I have a thief machine and an extra boardset. I thought I had heard you can do a ROM swap and turn a thief board into a nato defense. Anyone out there know if thats true?
Episode 60 I believe of the Arcade Outsiders, koolmoecraig talks about converting NATO Defense to Thief with a ROM swap, specifically $30 in ROMs. He'd probably be a good source to talk to.