speakers in the front door and rear (next to the rear seat) panels are both 6.5" speakers.

with the front doors you might have to cut a bracket out of MDF to make it fit cause the factory speakers, at least in my car, had this flimbsy plastic thing holding them in. you might be able to just remove to speaker from this plastic and use that to hold it.. might not be able to.

here is a picture of what i did. kind of excessive but i didnt want to use the flimsby plastic peice.