They just plug right in. I bought a pair at CarQuest. Just ask for 6v. sealed beam for your truck, and unless it is old stock, you should receive a sealed beam halogen.
I think I bought a Wagoner H6006. H being for Halogen.
If you want really bright headlights, you can replace the whole fixture with an aftermarket halogen 6v. setup. Expensive. I think Chevy of the 40's sells them.
Kurt