Running, turn signal , brake, lights, wiring

[roadking06]

I need assistance, 1981 chevy short wheel base truck. Problem with lights, brakes, running lights, turn signals. With the ignition in the off position the signal lights work both left and right. turn the head lights on the signals do not work at all, turn off the head lights the signals start working again. i believe that some rewiring has been done by previous owner, any suggestions, wiring diagrams that may help me trace out the problem?

[74chevy]

ok man i hope this helps you out

[roadking06]

Thanks for the wiring schemaic, going to work on it today.