If no one else beats me I could fax a diagram for a 72 on Monday.
The running, turn, brake lights are a different system than the rest of the 12v
in the trailer. So you only need that diagram.
A lot of problems like you are describing are because the 7 way tow/ trailer connections are not matched. Back in the old days the 7 way connections were not standardized like they are now and if you have a newer tow vehicle and the trailer has the original 7 way configuration it won't match. The good news is once you figure out the right wiring combo, it's pretty straight forward.