John - I can't be 100% sure, but in searching through Chevy and GM related Master Parts resources, it appears the original motor is listed as "counterclockwise". At one point in the mid to late 50's GM listed a common 6 volt replacement motor for the early Deluxe heaters like yours as GM #5047733. It replaced about 2 dozen like type 6v heater and defroster motors for Chevy's and other GM brands.
The 1957 Chevy parts book indicate a replacement for the original heater motor for Deluxe heaters from 1935-47 being listed as GM# 5047532. That's one of the many numbers the GM# 5047733 is listed as a replacement for.
I know it doesn't help a bunch with trying to find a 12v motor to fit that space, but wonder if acquiring one of a few NOS 6v motors I found currently listed on line for sale, if one of those motors could be used with a variable voltage controller like the one posted in this
Electrical Bay thread???
