Is the wiper motor crank arm original from the car, or did it come with the motor?
From the PHS website;
The crank arms also has a two letter code stamped, indicating what vehicle line they were for. The A bodies were letter coded AB while F bodies got letter code Y or T depending whether it was a Firebird or Camaro. The big cars got different codes, usually AF. We have included a chart to help you identify the wiper assemblies from their respective divisions in the 1970s.
http://phscollectorcarworld.blogspot...view=timeslide