We finished up a 1930 Plymouth "U" model early this year and one source we used was allpar.com and also Roberts Mopar Parts. There are several suppliers listed in Hemmings. Our forklift we use at work has a flat chrysler motor and they were used in dozens of industrial applications. Not many years ago and maybe yet the "donkeys" they use to pull aircraft around on carriers had this old engine. Steele Rubber is a little pricier than some but they had rubber for the 30 Plymouth. Also, Metro in Minneapolis will match up extruded rubber design if any of your old windshield, back window, or other rubber is in good enough shape they can get a cross section profile. Hope this helps some, Good luck; Evan