I had an odd thing happen to me yesterday. My '68 had her 50th birthday this week(11A build) & I wanted to take her out & give her a little birthday spanking before the snow flies!!! It was a balmy 44 degrees out but it was clear & sunny. It runs soooo good in the cold,especially with the OAI on it!! I had it warming up in the driveway & it just shut down. There was no power to the dash or starter. I know the car is 50 yrs old but the wiring is in excellent shape, it's never been cut or hacked. I left the ignition switch on & went out to look under the hood,everything looked ok, no loose or fried wires, no scary burnt wire smells. I got back in the car & as I watched the brake & gen lamps came back all by themselves & the car started right up?? It has to be the ignition switch,I replaced it & the headlamp switch 5 yrs ago with parts from Napa. I was scared to take it out but my neighbor owns a towing business so I took it out for a nice hour ride. It never missed a beat,it ran great!! I ran it pretty hard too!! There's nothing like some full throttle power shifting to put a smile on your face!! Maybe some "chineseium" assembly grease inside the switch got on the contacts & momentarily caused the connection to break? You try to cover your bases & replace things so you can have a dependable ride but the quality of some of the replacement parts we have these days really sucks!!! I already ordered another switch as I don't trust the one in the car anymore, hopefully I can get more than 5 yrs out of this one!

 

first thing I'd suspect is moisture/condensation on the contacts. (neutral safety, distributor, ignition etc.)
once it evaporated the contact was reestablished and all is well.

 

It may not be the ignition switch, I'd check the bulkhead connector/s under the master cylinder and the horn relay stud also.

 

Thanks guys. The horn relay wires were the first thing I checked, 68's use 2 small screws for the accessory wires instead of 1 stud like '69 up use. But then I remembered that the one wire I suspected powers the whole fuse box,it does go through the bulkhead. There are 2 other wires on the relay, 1 goes to the alt & 1 to the blower relay. If I disconnect the one for the fuse box, I lose everything in the car, ignition switch is dead,
courtesy lamps go out, & so do the exterior lights. The courtesy lamps & parking lamps were still working when the car died so I'm thinking that rules out the bulkhead connector. I've got a bunch of projects planned for the car this winter so I'll just add another one to the list!!