Short answer: No. The 40C is indeed a single-carb setup, but it would dramatically over-carb a 25/30A4, and you would need to fabricate an adapter plate, since the bolt pattern is different. The 40D is a 3-carb setup, with 3 small carbs. Those would not work at all. In any event, I highly doubt whether it would work out well. The guy is an idiot.