Ballast resistor wiring
At least on paper, this would have been the simplest and cleanest.
There's a chance that the voltage regulator has been changed to a solid state unit. This was frequently done when converting the ignition to electronic. It could be the same type as original (regulator controls feed to alternator's rotor) or may have been switched to the ground controlling regulator (has a triangular plug on regulaor).
Anyway. Your current problem is the ignition cutting out sounds like its related to things moving, so look for a poor connection in the ignition circuits.
At least on paper, this would have been the simplest and cleanest.
There's a chance that the voltage regulator has been changed to a solid state unit. This was frequently done when converting the ignition to electronic. It could be the same type as original (regulator controls feed to alternator's rotor) or may have been switched to the ground controlling regulator (has a triangular plug on regulaor).
Anyway. Your current problem is the ignition cutting out sounds like its related to things moving, so look for a poor connection in the ignition circuits.