A form 337 is not required to install FAA-PMA and TCCA-PDA approved parts. The TCCA-PDA is the Canadian equivalent to the FAA-PMA and is accepted by the FAA. 

Click here to see a copy of the Canadian Bilateral Agreement. 

Click here to see a copy of the American Bilateral Agreement. 

Click here to see an FAA interpretation. 

Click here to see an explanation of the TCCA-PDA acceptance.