http://www.toyota-4runner.org/audio-electronics/60174-urban-runner-radio-trim-ring-found.html
Check out that thread. It honestly is the best trim piece. It sucks it cost so much, but it has been worth it for me. It was so ugly before using the aftermarket trim kits.
I would recommend replacing the amp. It is not worth the headache of using the JBL adapter and all the issues that come with it. If all you want is to power the sub and the front speakers just get a 4 way amp and bridge two channels.
I started with using the JBL amp and after time realized...
I would like to also say thanks to whoever found this. I hated paying $90+ for a piece of plastic but it is well worth it. It worked perfectly with my Alpine IVA-W505.
SOLD - Stripped out everything related to the JBL system a few weeks ago and all I have left is the plastic sub enclosure. If anyone is interested I would like $20 plus shipping.
Also have the single disk JBL head unit for sale, just PM me an offer with that.
Warning! Did not fit 2005 4Runner with JBL Synthesis System
Tried to install the kit yesterday, but it does not look like it was designed for 2005 4Runners and down. I will post some pics when I get home from work. I would like to see if the shape fits 2006-08 4Runners.
Sorry no pictures. It is the all black wire. I just used a disconnect pair so if I had to pull out the head unit I could just disconnect the wire. It should be pretty straight forward. Search the Audio & Electronics forum on here too. It helped me a great deal with my install.
If your aftermarket harness does not have a wire for the power antenna you are going to need to hook up the power antenna wire from your new head unit to the #13 wire shown in the image below. This will give power to the antenna and give you a lot better reception. I just cut the wire right...