Not on a Ford (yet), but I probably will soon since I'm re-wiring 3 of my 6 trucks while replacing their dashes (one at a time). This shows 4 ways of doing it on a GM:
1997 Chevrolet Silverado 3500 Dash picture | SuperMotors.net The red wires are the new modifications. Each method is explained below the diagrams. On a Ford, it can be done by removing the upper steering column shroud (usually requires removing the ignition lock cylinder) and installing a simple shunt from the R/Y (headlight switch output) to the R/Bk (low beams) on the front of the MFS' lower connector:
1983 Ford Bronco Diagrams picture | SuperMotors.net To make it selectable, bring the 2 wires to a new dash switch capable of handling 10A. I'd recommend a switch with some kind of illumination so you notice when it's active, but not so bright as to be distracting.