as far as i know, the tweeters can be installed on the original spots, the cover(grill) just pops out if you use the small flat head screw driver. <- i got this info from the dealer, so i'm pretty sure they know what they were talking about.

yeah, it's true that you need to modify the aftermarket tweeter in order to fit into the spot, you must to strip out the outta plastic and stuff, just bare tweeter is what you need to install in the original spots.

$.02