lol - just came in from doing just this - like 5 minutes ago. I purchased a set from Best Buy earlier today and set out to "make em' work". I found a great thread where a guy named Henry T suggested hacking out the OEM speakers and using the plastic housing. This worked great and I'm glad I did it. Here's the URL:
Replacing stock 6x9s in 07 Tundra
I used a rotozip with the grinder attachment to take care of the plastic work. After I popped back on the passenger door panel I was a little concerned because there was a small gap between the panel and the door. I felt around the driver front door and it too had the gap (it had never been removed since I purchased the truck). Another suggestion is to make sure the new speaker fits absolutely flat against the OEM speaker housing. If it doesn't, you may risk having a bulge where the tweeter makes contact with the door panel grill.