Okay, here are the photos from my '99 Celica. Sorry it took so long:
http://riocar.org/modules.php?set_albumN...=view_album.phpSome corrections and additions:
I used a scalpel (X-acto knife) and a razor saw to modify the plastic. If you have a Dremmel, that would be easier. You need to leave small rounded edges in the corners - not as rounded as the unmodified plastic. Let the Empeg fascia be your guide. Take your time.
I said that I cut off the Toyota wiring harness. I mis-remembered this. I actually used a Toyota-to-DIN harness adaptor from a car accessory shop (Halfords, I think). I did dismantle the Toyota CD unit harness but it turns out that both the control and the audio signals are pretty non-standard.
The power from the Amp was spliced into one of the thick power cables under the steering column. If you want to do this the same way, send me a PM and I'll have a routle around and report back exactly which one I used. The ground from the Amp was attached to the bodywork using a lug and an existing bolt under the carpet near the door. Use a milliameter to check that there is a good electrical connection between the wire and a known good grounding point after bolting the other end to the car.
I'll post an exterior shot at some point in the next few days.