You can find a list of the Canadian body parts in the CMAFF library. Look at the top parts for an open car in the July 15, 1932 file. The only reference to part numbers with 42175 are curtains (page 66) but nothing for the frames that you mention. It looks like anything with an AR designation is for a 40A model (28-29) Have a look and perhaps you can figure it out. I have access to all the CMAFF literature but could not find any other information on this. Sorry I can't be of more help.
https://www.cmaff.com/Library/Canadi...y%20Parts.html