I found a brown wire that works for my park light/backlight.
The accessory wire isn't absoultely necessary.
I really need to locate the horn wire. As I understand it that wire activates the horn when grounded so it won't ever be hot in the cab. That's fine I can change a jumper to activate on ground. It makes it hard for stupid people like to me track down the wire though. I understand that after it goes through the relay then the wire is obviously hot to activate the horn, but I didn't want to have to go outside the cab to hook into the wire.
I need to locate the wire that tells the system the driver door is ajar. It can be a positive or negative wire it doesn't matter. I can make it work either way.