Hey oilslick,

Do a search of this topic and you will find alot of good advice. I just put in a new alpine in my 84 300d and it was a pain in the neck to figure out the wires. It is late right now but i did post in the past all of the details. Here is what I can remember. Actually I cant remember without looking it up. The main problem I had was finding the power antenna wire. It is customarily blue and it is blue on the benz however it is wrapped in black shrinkwrap so it looks black. I believe that is is the blade connector that inserts into the back of the grand prix.

I rewired all of the speaker wires bypassing the fader switch as you will loose power if you go through that. The old radios are 2 channel with a resistor which seperates them into front and rear. I recommend that you bypass that stuff. It is a pain as you have to run wire to the rear deck.. I removed the rear seat, which can be a pain in the neck, but since I did it before when I changed the shocks. I would also run some rca cable back now if you are ever to consider amping the rears as you have it all open.

Soder the wires together, using flux, and have some fun....

good luck,

bob c