I am selling speaker adapters, which allow you to install 4", or 5 1/4" speakers in the rear doors of 96 - 02 4runners. They are made of sturdy 6mm PVC. You can't replace these speakers without using an adapter. They are a toyota speciffic size. I am selling them for $6 a pair, plus $4...
rear speakers
careful wehn getting new speakers for the rear doors. they are a custom size. you can put up to a 5.25" speaker in there with the right adapter. here is a websiote where i guy made his own adapter.
http://www.amug.org/~sschaefer/polk.html
you can save yourself the time, and...
if you don't wanna put spacers in because you are worried about them hitting the grill, you can always get very thin ones. you can get 1/4" and 1/8" spacers from www.mjmautoinnovations.com