Lexus LS400 radio harness diagram

Can anyone help me with the wiring diagram for a 1996 Lexus LS400 radio. Any help would be great. harness diagram or wire color, whatever you have. I'm trying to replace a dead radio w/ an aftermarket radio, without having to mess with the factory amplifier. Since the radio is dead I have no way of metering its outputs.

For your power wires and such you can access them up front, grnd, acc, constant, and ant/remote turn on. The speakers you will have to find the factory amp (usually located drivers side trunk under the disc changer) and bypass the amp and run your 4 sets of speakers wires from the amp bypass to the new Headunit. you can use a tone generator or a 9 volt battery to find the speaker wires and a test light or DMM to find the power wires up front.

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My mechanic told me, "I couldn't fix your brakes, so I made your horn louder"

I was hoping to go high/low level into the wires in the dash, or use a converter and go into the wires in the dash, without having to take the rest of the car appart. If anyone knows what wire are what in the dash i'm still interested. I'm trying to keep the factory amp intact, otherwise i'll have to redo the sub and mess with crossovers.