hi Jeff,
Get a dc voltmeter, then near the fuse box check and try to idenitfy the fuses/wiring related to the ignition coil and the headlights.
You need a 12V dc coil relay having a normally open contacts, rated at least 20A.
Ideally the new relay coil would be connected to a +12V ignition wire [ and the other end of the relay coil to chassis] , so it that the relay becomes powered when the ignition is ON.
This will turn on the relay,,, the wiring for the headlights will be 'cut' and connected to the relay contacts.
So,,, ignition ON, relay ON,, headlight circuit
enabled via the relay contacts, you will still need to switch on the headlights with the normal switch, when the headlights are required.
If you forget to switch off the headlights when turning off the ignition the relay will open switching off the headlights.
OK.?