[Marshall V. Daut]

I agree that PERHAPS pulling the head was a bit premature without first running a couple other checks (compression, distributor shaft rotation, starter operation), but the situation as it stands now is not without an advantage. With the head off, the OP can push the starter rod and check the operation of ALL the valves, as well as whether the starter actually turns the engine over. It's highly unlikely that between the time the OP parked the car in the barn and when he went out the next day to start it that at least one valve in each cylinder became stuck, a couple valve springs broke or that the head gasket blew out in each cylinder. Pushing the starter rod when the head was still in place would have told him whether the timing gear was stripped, the head gasket had blown and/or whether the Bendix drive was inoperative In all three cases, the starter would have turned the engine over at a noticeably faster rate than usual, which the car's owner should have recognized by the difference in sound. One poster already suggested this. Too late in this case, but a good sleuthing method to keep in mind for future problems of a similar nature.
If the valves open and close through a few revolutions with the starter, the OP can observe their operation and eliminate stuck valves from the equation. If only a few valves open and close as they should, but others remain stuck open, then there is a problem possibly with them sticking in the guides. If they don't move at all, the timing gear is stripped or possibly the oil pump drive gear is stripped or the shaft's pin sheared off. Easy to spot this by re-inserting the lower distributor shaft into the engine (assuming there is the two-piece shaft in place) and push the starter rod. If the lower distributor shaft doesn't turn, then we're back to a stripped timing gear or a problem with the oil pump drive. You could also just look down onto the distributor shaft hole and see if the oil pump drive gear is turning. That requires more gymnastic ability while holding down the starter rod than watching the lower shaft turning above the deck of the block.
If the starter spins, but the pistons don't go up and down, the starter's Bendix spring is either broken or a drive mounting bolt has sheared. Easy to check this operation.
If all the above work o.k., then about the only thing left to explain zero compression is a blown head gasket, unlikely as that would be. But all four cylinders blowing out - while the car is parked? I'm leaning more towards a stripped timing gear/oil pump drive or trouble with the Bendix. Pistons go up and down, the valves operate fine = what else could explain zero compression - if a zero compression situation actually did exist and the signs were not misinterpreted?
Marshall