It is hard to say, sitting here….But if you have arcing at the choke solenoid plunger, that would seem to indicate that voltage is looking for a path to ground from the carb, across the gaps between the plunger and the choke solenoid, to your good ground on the lower pan. (I hope there is no GAS in that carb, yet!) As for arcing at the base of the starter, you may have a secondary connection problem, possibility caused by your nice paint job. Like Frank said, a voltage drop test or two across the suspect areas will tell the tale. To start with, put one lead of a volt meter on a good, clean, bare spot on the block and the other lead on the ring end of the ground cable bolted to the lower pan. Crank the engine and observe the meter. Any movement of the needle (or digital voltage reading higher than zero) indicates you have a problem between the main cable at the pan, and the block.
Long live American manufacturing!
