1994 Mitsubishi Truck Random Death

This little truck has developed a situation where you'll be driving along, everything normal, and all of a sudden it's as if the switch gets turned off. Dead. No power anywhere (ignition switch, radio, lights). Totally dead. Then, after some apparently random amount of time, it'll work again just like normal.

This happened just the other day when we were driving 65mph down the freeway. All of a sudden I realized the engine had died and there was no power. Rats! We had to get a tow home.

I've already replaced the ignition switch and the battery.