If you look on the outside (engine side) of your firewall, you will probably find little divots to locate the holes, assuming a factory radio box and a factory heater. Some other GM makes with FIsher bodies had that. If the little divots exist, you should be able to match them to the studs on the back of your factory accessories and see whats up.
I would GUESS that the heater is on the right side, the radio to the left, and the external speaker, if used, in the middle or slightly to the right. Gene will probably know for sure.
I did not think there was windshield ducting in 1936. so I would like to learn about that as well.
I see you're in Canada. Is it a Canadian model? Is it Standard or Master? They are very different cars in the mid 30s.
Last edited by bloo; 10/21/19 03:20 PM.