[blucar]

To the best of my knowledge the '39 and earlier, ie; any vehicle with a crank-out windshield did not have builtin provisions for defrosters. Ford did not offer hot water heaters until 1939, prior to that they were the manifold hot air heaters.
Ford did offer an accessory defroster unit that attached to the face of the dash extending up to the windshield..
The majority of the accessories offered by Ford were dealer installed, the reason being to keep the base, and unladen weight price as low as possible.