Springfield XD9 & XD40 compatability

Hey all,
I own (and absolutly love)an XD9. I would really like to also have the 40. I know there are kits to make the 40 a 9, but if I bought a 40 slide and barrel, would it mate up to my 9's frame? I know they are the exact same weight/size, but I am unsure if all the other "goodies" are the same. Thanks!!