You need to share some details and pics.
My tweeters are the Polk Audio ones that came with the MM series component speaker set.
http://www.sonicelectronix.com/item_...io-MM6501.html
I have them surface mounted over the same spot that the factory tweeters used to be. I was on the fence which way I wanted to go, but chose to surface mount them allowing me to have a little more flexibility in aiming the tweeters. The surface mounting allows them to swivel a little bit in their mounting cups.
Someone else chose to un-case the tweeters and mounted the tweeters in the factory location. So yes it can be done that way.