Well, I've got a 2 door spoiler on my 4 door. I saw it side by side with a '00 white sedan with a stock 4 door spoiler on it last week and there definatly is a difference. I didn't get a chance to pop the trunk to check out how his was mounted but I can guess. You can put a 2 door spoiler on a 4 door. It just takes a little tricky drilling. They make spolilers specialy for sedans so I would look into getting one of those. if all else fails then get a 2 door spoiler and figure it out. The guy with the stock 4 door spoiler didn't even notice that mine was a 2 door version untill I pointed out the differences. Their is probably less than half an inch difference on both ends of the spoiler. its really really subtle. You'd have to know that it didn't come that way to tell the difference unless you were comparing it side by side to a factory 4 door spoiler.
I'd post pictures of it but this board doesn't seem to want to let me post pics from my MSN album. :(
You'll just have to click this link instead.