I have now found via crutchfield that my dash speakers are the 4 1/2" and the rear panel are 6 1/2", but aren't there speakers in the top by the rear window? Where can I find out what speaker will fit a limited 4runner?

 

there are speakers above there rear window...but they are only tweeters...if these are in your runner than you have an upgraded factory sound system with a rear amp and crossover built into the housing for the rear speakers in the side panels...i ripped out the stock speakers and amp...left the crossovers and flush mounted 6x9's fed by an amp mounted under my passanger seat...the sound is great cuz' having the tweeters up high in the back raises the rear soundstage up to ear height as opposed to leaving it all lost behind the rear seat...

 

eggcelent!

I had no idea that it was even an upgrade... So what type of amp is it? how big are the component speakers in the rear? Tweaters?

 

i think the component mid-bass woofers in the panels are 6.25's...tweets are pretty generic...'bout 1.5's...amp and crossover is all toyota factory stuff...all the writing is in japanese...which i couldnt make heads or tails of......heres the deal though...if you attempt to use the existing toyota amps and crosses...and replace the speakers you might run into trouble...especially if you also replace the head unit...for example...the amps and crosses are all set up for a very low power input coming from the factory head unit...once i replaced this with a high power aftermarket head...the signal was too "hot" for the amps and crosses and they basically cut out everything except for the high freq...in my opinion...your best bet is to just get rid of all the factory stuff and put in some good gear...a decent amp wont run you that much and in the end youll be way more satisfied...if you try running good speakers off of the crappy factory amps...the amps will max out and cause distortion before your speakers even reach their potential...