When I got 'the wrong' tranny for my 300, I was told it was off a 240. It had different cooler lines and dipstick. The mounting was different, and since those items are rigid, they wouldn't have worked without swapping them out for 240 cooler lines and dipstick as well.
I've been told it'll work, if you can install it. In fact, it's probably a better bet in some ways than the 'right' one, as the 240 would have treated its tranny somewhat more gently than a 300 would. Still, I didn't wanna screw with 'making it work'. I paid $550 for a good used tranny, and I wanted the RIGHT one, damnt.
Good luck!
Ash