With a '37 or '38 truck, if the windshield fogs up you just crack the windshield open. You don't need a defroster. You would really have to alter the dash to make room for add on defroster ducts. There just isn't the room like the later dashes.
Kent


1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix