I found it.
It's on page 12-27 and 12-28 of the 1942 shop manual.
http://chevy.oldcarmanualproject.com/shop/1942/42csm1227.htm

There's a good wiring diagram that shows that if you don't have the switch, one of the distributor terminal should connect to the coil (-) and the other should connect to ground.

The purpose of the switch is to reverse the current flow across the points each time the truck is started, to equalize wear.

regards,
Leon