swaping a 360
you WILL need different motor mounts and a different 360 balanced flex plate (like from B&M) since 360s are externally balanced. 340/360s share different motor mounts than 318s. Yank the 904 out when you pull the 318. I myself wouldn't put a motor than i haven't gone through in my car..Idk the story on it, but i would atleast pull it apart, check bearings and clearances before going through the trouble of sticking it in there and there being a chance of an issue and having to yank it back out. Don't get impatient and try and 'get the 360 in' as fast as you can and skip the important steps of checking things out.
Just my .02cents