How many brake line and fuel line clips do you need to attach the lines to a 1966 f100?

There is no set answer unless you can see where the original clips were located. Ideally the clips are used to keep vibration to a minimum thereby reducing the possibility of wearing through each other and/or frame, etc. I have seen them as close at 24 inches and as far as 36 inches apart. I would start at back or front at 24" spans and when your done, wiggle / tap / shake lines and make sure they don't hit each other or come in contact with frame, suspension, etc. In addition, older models used steel clips that would contribute to corrosion, newer plastic clips can be purchased to eliminate this possibility.