you really can't go wrong modernizing that old wiring - it'll be safer and more reliable. Trust me on this one: if you do just the headlight wiring - 6mo. from now, you'll wish you did the entire harness. link to EZ Wire - Home
or there's this - 1953-56 Ford F100 Kit | American Autowire - probably a more direct "plug and play" option
and this Wires & Wiring Harnesses - Mid Fifty F-100 Parts