2004 Chevy single cab pickup stereo

okay so there's a double DIN radio in it and a different harness that resembles one of those fancy Buick harnesses. What else is going on in that truck? I looked at the radio harness and identified front and rear speakers. However there are 3 new wires that I saw: a bigger red wire, about 16 guage, and then a smaller red wire, about 18 or 20 guage. Then there's a black wire with a white stripe, which I am assuming to be the ground. I have to put an Alpine in the truck so I need to know what the customer is getting into.

Nothing crazy like factory amps or anything, huh?

hope this helps, this should be similar to the 03 in that a factory relocation is needed if the customer wants to maintain keyless entry, door chime . the factory radio is needed also for diagnostic purposes by service techs. if these are not an issue, then the harness for a late model geo or gm import schould be the same to match up to the 04. now the only thing is acc power needs to be tapped from the ignition harness under the steering column the harness for this should be directly behind the fuse pannel and it will be the larger brown wire in the harness, or with a dmm the black box near the brake pedal remove the cover you will see several small pins test each pin near the bottom for 12v switched when located tap on with a small female conn (this however does not always work because the voltage is sometimes lower than neeed to switch the radio on) .

   hope i was of some help