The floor dimmer switch turns the headlights from low to high beam. Mine sat for 20 years and all I had to do to get the headlights working was spend a couple hours cleaning the connections. If you do what sharps40 said you should be good. Here is a color coded wiring diagram from the stickys that may help.
http://67-72chevytrucks.com/vboard/s...d.php?t=378484