Rob,
You can find a variety of reference materials and links that might help you in your search at the website '1946-48 Plymouth Nostalgia & Reference'.
http://www.searcher.com/P15.html
If you aren't already, I highly recommend becoming a member of the Plymouth Owners Club. Membership includes an every other month magazine 'The Bulletin' with a very good parts wanted/for sale classified section.
Best regards, DJ