There are so many things that you can do with these year trucks. I have a 1968 that I left stock just because it already had all the goodies. (396 v-8, A/C, Tachometer, cruise control, wood bed, 400 transmission, and a CST truck) But you can drop them, put disc brakes on them like Wrench bender said, put the gas tank between the rails and get it out of the cab if you want. They look great stock, or they look great lowered, shaved, and rodded.
Go to your local bookstore and pick up a Custom Classic Truck magazine, as they show them sometimes stock or modified. Good luck with your project!
Tom