Yeah I'd have to sortof agree.But since the engine cranks, the starter is seeing ground. And the starter is connected to the battery negative through the tranny to the engine and out the negative cable.So that entire part of the system is seeing ground, and anything attached to it. The coil and dizzy do not care about the engine being grounded.That kindof leaves the ECU hanging out in the breeze. So my guess would be that the body ground is compromised. There should be a ground strap from the rear of the passenger side head(V8) to the firewall, and another from the battery to the radiator core support. Check/clean these, and also the ECU must be grounded through the mounting screws. Without the body grounds, the ECU could back-ground through the headlamp filaments or the domelite switch at the door. At least until they all burn out. The headlights have their own ground right at the core support next to the battery.
But, I must say; since the headlights are working, that must mean that the core-support ground is working, so now that kindof means the grounds are all ok.Nevertheless, I would start with cleaning those first.
So once the grounds are known to be good, come on back; I think the problem may lie elsewhere.
