Sometimes you just have to do the work. I was still having some problems with the electrical system. All the lights and things were working but when I switched on the headlights, after about ten minutes the lights would start to flash off and on. None of the fuses blew but I couldn't leave it like this. I decided that I had to remove the entire under dash harness and inspect and test it. I didn't think that there was an actual short circuit but there must be a lot of resistance somewhere in the harness. I set up a couple of folding card tables and spread out the harness to visually check all the wires and connections. I have found that setting up a card table and chair in the driveway next to my car makes everything easier and more comfortable. I can set up the repair manual and tools on the table and inspect parts while seated.
There were some iffy looking splices and connectors that I pulled on to be sure that they were secure. I resoldered anything that looked suspect. I had removed the light and wiper switch and the fuse box was still attached. I checked the function of the switches and checked the circuits using a test light and multimeter. It's a good idea to use a lower amp power source like a trickle charger or the two amp charge function of a battery charger, you don't want to fry the wires if you make a mistake. I also tried to loom the wires a little better to make everything neater. I ran the looms through some black plastic conduit for protection and appearance. I coudn't find anything that was shorted out and the connections to the firewall connector looked okay also. I reinstalled the harness and tried it again. Same result. For some reason the headlights were drawing too much power for the built in circuit breaker in the headlight swtch. Hmmm. Now I had seen that the headlight sealed beam sockets were pretty corroded and didn't look much better after I tried to clean them. ( My car was missing the inner fender splash shields that would have kept water off the headlamp plugs). The factory headlamp wires that fed the front part of the harness through the firewall connector were very thin, maybe 16 guage. I could imagine that it wouldn't take a lot to raise the resistance enough to possibly cause a problem.
I had gone to the Goodguys show in Pleasanton and had seen several vendors selling wiring harness kits which might well be the next step. Still I didn't want to spend 700.00 if I didn't have to. Over the years I had read several articles in CarCraft magazine about improving the headlight function of old muscle cars. The lights were dim because they wern't receiving the full twelve volts that was needed. Over the forty some odd years these cars had been in use, the wiring harness had degraded and couldn't pass enough juice. The fix was to run a heavy wire directly from the battery to a set of relays that would supply full power to the headlight elements. the existing wires would only trigger the relays which require much less power. I decided to make up a new harness that bypassed the existing wiring to the headlights completely. I figured that if this didn't solve the problem than I would run new wires directly from the headlamp switch completely bypassing the firewall connector and related wiring. I went to a NAPA auto parts store and asked for some relays to wire up some driving lights. I bought the relay and the matching prewired plug. Not only would this look neater and more professional; but it would provide better protection of the contacts. I needed two, one each for high and low beam, as each realy had two output circuits. I also bought two new headlight element sockets. I mocked up the placement of a 30 amp circuit breaker and the two relays using a 2in.x6in. piece of wood as a mounting plate. Using this I looked for the best place to mount the assembly under the hood. I chose to mount it on the inner fender panel ahead of the left shock tower. After I finished running the wires I routed them and formed them into a preliminary finished harness. Now another test. I fired up the car, turned on the headlights and let it idle for ten minutes, no problems. I took the car out for a test drive and a half hour later I pulled into the driveway with the lights blazing brighter than ever.
Any long trips are just a series of shorter ones. If your car can handle a 100 mi. trip reliably, without requiring the following:adding multiple quarts of fluids, (except gas in the tank) changing fouled plugs,clogged gas filters,flushing the radiator, replacing the thermostat, fanbelts, water pump, jumping the battery,replacing blown fuses,rehanging the exhaust system, patching the gas tank,rebuilding the brakes, replacing tires worn to the cords, the clutch isn't slipping, the auto trans is still automatic, rebuilding the brakes, replacing the generator/alternator, your turn signals, headlights, signal lights, windshield wipers, heater still work, you may have a driver!
I think that it is real important that the car track as straight as possible, and that the steering have only a small amount of freeplay, (although I drove some sloppy junk when I was younger). This is important, because while you may feel that you can live with it on short trips, on a long trip, due to fatigue you might let it drift way off line and then suddenly overcompenste to pull it back in the lane. Every bad trait in the steering/suspension will come out and bite you in the ass and you could lose it! Don't take a chance with your and your families' lives, not to mention anyone unfortunate enough to be around you if that should occur. Be sure you have good seatbelts.
A final thought. If you drive the car for an hour at freeway speeds and then stop, and it idles smooth, doesn't heat up, and will start right up in five minutes, that's a good sign. Enjoy the drive.