I need help......bad

my son and I started this resto on my 76 Duster. He was a mechanic, I am not.Car is completely done except for some wiring in the engine bay. He is no longer with us and I am left to figure this out. There is a black wiring block in the center of the firewall that has 4 or 5 plug ins to it. I know the first one on the top left goes to the wiper motor. the rest I have no clue. can anyone tell me where the rest go. Is there any wiring diagrams out there that will show me this or how do I go about getting this figured out. I have all the wires that plug in there its just I dont know where they go. Any help or guidance would be greatly appreciated. Thanks,Bill