Steve - YF3211S is the model supposed to have been marketed as a replacement for mid to late 50's 235's with Rochesters. It has an auto. choke. I have no way to check this info, but that's what most sellers say. I have run one on a 235 & it worked OK for me. The 4 digit # followed always by an 'S' is what most guys use to ID them. Doug
