Busboy

Almost.. Keep the harness you have, as you said the park lights are OK until you use the high beams. As the wire for the headlights is poor to say the least, install relays to run your headlights (hi and lows) and new wire accordingly. Some of the parts houses sell relay kits along with a new headlight harness. Just pick the wires a you need from the back of the light switch and cut the old output from the switch.