What causes a 1968 Ford F100 engine to have no spark? The voltage to the coil is < 2V with a new battery. The truck shot a blue flame through the carburetor the last time it ran, after that the battery died.

Sounds like the distributor may be installed out of phase, which is dramatically affecting timing. Remove spark plugs, set #1 cylinder at TDC, and ensure the rotor points to the #1 terminal inside the distributor cap.

Your reasoning is flawed. You have multiple problems.