Car died for 20 min after a few bouts of hard acceleration

Well, if your 67 was converted to hydraulic lifters, my guess would be that the lifters pumped up, and the engine lost compression. Then, after some time went by, some of the lifters bled down enough to make compression and she started right up.
But, your 67 should have solids in it, in which case, I have nothing to say, except, check the fuel-tank vent, and the shape of the tank; the pop could have been an imploding tank wall ..