You know, I suppose at this juncture, it doesn't really matter too much what battery is supposed to be in there, since it's probably missing the OEM terminals on the leads, since it's got a Ford square post battery in there. Even if it did have the original terminals, they're JIS sized, so it'd be a struggle finding a battery with JIS posts anyway. Just find something that fits, and run with it. Maybe something from Odyssey's Performance Series range?