Well, I'm bringing back this thread because I may have got some bad information. I was at the dealer today getting the oil changed and went out on the lot and looked at the 4Runners. They had an SR5 with the basic stereo parked next to an SE with the non-JBL 6-disc changer, and the way they fit in the dash was identical. Both had the "recessed" type of fit. I could see no difference in the plastic piece that surrounds the stereo. The JBL stereos that I saw had a "flush" type of fit, with an obvious difference. Oh well, the 6-disc changer that was on e-bay sold a while back ($30) and I already have my Scion 1807 ($38 shipped off e-bay) although I haven't installed it yet.
Now that I have these MP3 CD's figured out, it kind of makes the changer unnecessary, in fact I like them better with the artist, song title, etc. display. Bottom line is, Momma's happy, although she is not really wanting me to install the Scion radio because "I just got all the buttons figured out" on her current stereo.