[wraprail]

yup. Hi/Low on/off
I should mention that I spliced mine right at the dimmer. (steering column)
As for Relays,
I believe that anytime you upgrade your headlights whether Halogen, HID or whatever you should awalys
install relays. You can buy a pre made harness or pick up a couple relays and do the wiring yourself.
For those who don't know, the headlight circut on our trucks suffers from high resistance and excessive voltage drop
when used with anything except the stock sealed beams. The power has to travel through the headlight switch, Dimmer switch
fuse box many connections with very small gauge wire. By using a relay with the proper connections and wire size you bypass
the troublesome connections and power straight from the battery to the lights.
As INSIDIOUS mentioned, HIDs require an inital surge that the factory wiring has trouble providing and Halogen draw alot
of power all the time they are operating.
Even with the factory sealed beams you would see a noticeable difference in brightness just upgrading the wiring and using relays.
And the older the truck the poorer the wiring and bigger the improvement.