My factory wiring is ackward on my car. please help?

I have a 1978 Chevy Caprice & I just took the a-track/radio out. theres only about 7 wires that I can wire into. There is no harness at all to plug a new deck into. Now I know that there should be a total of 8 speaker wires (left rear neg.,left rear pos.....), and about 4-5 other ones (power, ground...) these are the excat colors behind the old factory radio right now..(lightgreen,darkgreen) (black,black) yellow, gray, orange. what the heck?! im so confused. the manual comes with no wire diagram and I really dont want to go to a shop to spend about $50. will someone help me turn this situation around. please? can someone tell me which wires are which? or how i can test them? i know that the rgreen ones are the right front ones, and the black ones are right rear ones. i tested it with a 9 volt battery and the speakers crackled. but where are the other wires????