No clearance/running lights?

Yes, sounds like a switch or if it has a fuse or circuit breaker check it.

I think I found the fusible link off the starter relay - had to go thru the doghouse. However, I don't understand the link - it doesn't have a fuse. When you take it apart, it has a male probe in the bottom half that mates with female hole in the cap. 12V light probe didn't light up when I touched the male probe or the female probe while ignition was off. However, when I turned ignition on, male probe lit up. So don't think that was it.

So I took a fusible link and went from a "hot" source at fuse box under the dash with ignition "on" to the positive side of the fuse holder for the clearance lights.

Clearance/running lights lit up. I'm bypassing the light switch - doesn't matter whether it's on or off, the clearance lights are on.

Would this suggest light switch is the problem?

I wood replace the flasher relay and or turn signal relays. It might cure some of the problems

Well, I traced the positive battery lead and the positive starter lead and they come right up front of the radiator to a post. I took a picture but for some reason, I can't get skydrive to share this evening. Anyway, I'm not finding a fusible link along those two paths and I don't know where to turn next. Using 12V light probe, the posts that these both are connected light up.

Follow the chassis battery positive lead or follow the large cable back from the starter.
The relay should be on the radiator cowling or brace.

Using a light probe, the only two in the fuse block that do not light up are the running/clearance lights fuse and the dash light fuse. Everything else works. The emergency flasher is good, but only flashes up front outside - not the rear lights.

Where would I find this fuse link that's at the starter relay - not sure where the starter relay is - up front?

Turn signals, gauges and wipers all work off the ignition switch circuit.
Taillights and dash lights work through a portion of the fuse block that is hot all the time. They normally are on two different circuits from the battery. Could even hasve a main fuse on the fuse block, but i beleive it is a fuse link by the starter relay.

The turn signal fuse, the gauges fuse, wiper fuse, etc. are all in the same fuse block and they work. And using a multimeter, I was getting juice to each side of the fuse clip. However Jim, you brought up a point about one bad bulb causing circuit to shut down - as I recall back in the 70's, that was a common issue with Ford trucks anyway - if a taillight was out, everything was out. Had it happen in a '75 and a '79 F150. Thanks for the follow up guys - every little bit helps.

Is there power to the fuses?
There is fuse links near the starter relay on Fords. The fuse links supply power to the Ford chassis fuse block.

If the fuse is good, then you have an open somewhere in the circuit. This will be a tough one to track down. I wouldn't think it was the light switch if the hazard flashers aren't working. But without a wiring diagram, it's hard to say.

If it were me, I'd get a 12v light probe. It's just a light bulb with in a transparent plastic handle with a sharp probe on one end and an alligator clip on the end of a cord. I'd hook the alligator clip to a good ground such as a screw that is in the frame. Then I'd start at the fuse box. Turn the key to the on position and stick the probe on each end of the fuse clips. It should light up on each side. If not, you either have a bad fuse or a bad connection. If that doesn't detect it, I'd start probing wires and light sockets all along the wire loom until I found the offending open circuit. Quite often, a connection can come loose somewhere.

One other thought. You don't suppose you have a bad bulb somewhere in the circuit that could make the whole circuit shut down do you? I've never seen that happen on a 12v system, but you never know....