I looked at the wiring diagram for a 42 pickup --
http://chevy.oldcarmanualproject.com/electrical/wiring/pdf/42truck.pdf

I see the problem. You have a polarity reversing switch between the coil and the distributor.
The minus side of the coil goes to the polarity reversing switch, which I believe is on the starter.
( https://www.chevsofthe40s.com/detail/5958.html )
The two wires form the distributor also go to the switch. I've never seen one of these switches, so I can't tell you which terminal is for the coil wire.

I hope its marked well.

regards,
Leon