67 Dart Headlight Switch and Connector Recommendations?

Dana knows about relays!
I put together my own, and I've seen Stern's kit and Yule's ready to run harness. I'd say both are really good quality and would recommend either one. Stern's may provide some more flexibility in terms of hiding the relays and the wiring to keep the engine bay looking stock.

One thing worth mentioning. The headlamps supplied in 1967, and up through around 1973, drew less current on high and low beams than the lamps that followed.
Those in turn were replaced by halogen lamps that drew less current on low beam, but more on high beam.
Point is a factory correct lamp doesn't put the load on the system as many of the replacements.

Headlamp Lamp Chronology and nominal power consumption.
6012; 40 Watt low, 50 watt high beam.
6014; 50 Watt low, 60 Watt high.
H6014 (Halogen); 55 Watt low , 60 Watt high.
H6024 (Halogen); 35 Watt low, and 60 Watt high. (except GE's nighthawk version)