Has anyone swapped the 4x6's out in the doors for a different size speaker? And to do so is there any modification needed?

I got pioneer 6 1/2" to fit in there fine no modification.

The opening in the sheet metal is a round hole, that can easily accept a 6.5" speaker. You must be concious of the mounting depth of the speaker. I think that there is just under 2" of mounting depth before the speaker magnet would hit the window glass. You can buy/make MDF rings to use as a spacer that will give you more depth.

^^^ Yep X3

Alpine type S 6 1/2s front and rear

Thanks for the info, I'll probably be going with pioneer 6.5's front and rear thenhttp://i43.photobucket.com/albums/e387/slw_tsi/Emoctions/thumb.gif

i always had to cut away at the inside of the speaker grill so the rubber surround on my speaker wouldn't fart up against it.... just took a dremel to it... especially if you use a spacer kit..