Retread,
I am not sure if a true "how to wire" book exists. There are standard wiring practices that apply to most situations.
These would include fuses for protection, wire capacity for the intended load etc.
It appears you have your harness almost in, so your feet are already wet, so to speak.
I have enclosed a link to Chevrolet wiring diagrams. It shows how Detroit did it.
I would take a piece of paper and make a list of all the questions I had about my wiring so far.
Attack them one at a time, doing some research and looking at factory schematics to see how the factory addressed them.
It sounds like you were aware of the lack of a horn relay...this would not be obvious to everyone.
This forum is always here to answer your question or to confuse you more, which I usually have a hand in!
http://chevy.tocmp.com/chevywiring/ Stuart
