Yes, they are different. Novak is wrong. Maybe they are thinking of the later 231 V6 and 225, which have the same bell pattern. Not sure, but I would expect the transmission-side pattern of the 198 and 225 bells to be the same. Don't know if they are the same depth, but it's likely they are. The engine-side bolt patterns are clearly different. If the transmission-side pattern is the same, and the depth is the same, the 225 uses a common BOP (Buick-Olds-Pontiac) GM bell, and a BOP bell should be easy to find. Just FYI - better to start a new thread with your question than to revive an old thread.