Can someone please tell me the difference between these two transmissions? I am trying to buy a tranny from a guy long distance. But, I didn't like that his looked different than mine. He claims, as I do about mine, that his is an M41. I know that the shift plates are interchangable, that's not a problem. My concern is that the cast ribs on the sides of the casing are clearly different. Are these two different transmissions? Are they early and later versions of the same transmission? Please look at the pictures and let me know what you think. Please use the correct # tranny for clarity (you'll see). Thanks all.