help on Stock A/C on a 78 Big 10

[Chevyguy111786]

I just bought a 78 Big 10. The big block was removed and replaced with a 305. It still has the stock components and i'm in the process of converting to 134a. Does anyone have a wiring diagram for the ac system? The a/c unit won't turn on and i can't charge it until it does. I know i'm missing the wire that goes to the compressor and want to check to see if i have all the other and if they are run right or not. Also any other tips or help would be nice. Thanks in advance guys.