I took a look at it and it's not too encouraging. It's a 3 1/2 inch in the factory location. With a bit of cutting, you could possibly put in a 4 inch but thats a lot of modification to put in a marginally better speaker. Kind of a waste of time if you ask me. One other option would be to build a fibreglass enclosure coming out of the existing stock location and fit in a 5 1/4 inch tweeter combo. The space is definitely there. Hardly stock in appearance and not for everybody, but I'm running a DVD Audio show type system in my 4runner so I will probably do it. (I won't do it until next winter, after all the car audio shows are over).
