I purchased some headlight rings from http://www.franklintruckparts.com/fons.html

These worked perfect for my 37 plymouth.. They have the running lights/turn signals led built into them.. They aren't too expensive.

Also check with- http://www.srpmstreetrods.com/srpm/1937-plymouth-car-ff80808117344aab0117418a15d73e7d-c.html