I read that the SEGA I/Os can also do Capcom games, and that buttons 4+5 for both 1p+2p are carried on the JAMMA edge and button 6 you wire from a pin on the I/O.
I know my Blast City is wired for button 4 and 5 properly on the JAMMA edge cos I've used it successfully for Neo Geo at least.
But...