318 poly wide block

I need some advise, I recently bought a 1965 dodge s400 (it's a school bus) with a 318 poly engine. I need to replace the clutch. The only clutch I can find is for a 318 la engine. I need to know if the transmissions were the same or at least similar enough for the clutch to work. From my understanding there are a couple of different transmission that the 318 poly could have. I can't say I know which one I have, I know it's a 4 speed. But there is so much old grease on it I can't find any numbers. I am hoping someone can educate me on this a bit better. I've been searching forums but most people talking about the differences in engines don't talk about the transmissions.