My cousin just bought a 1951 Desoto with a straight six. The guy told him its a 251ci. The parts mag we have been looking at from Kanter auto doesnt show a 251ci in a straight six they show a 241, 236, and a 228ci from 1937 to 1954. Across the top of the head it says spitfire in raised letters. Anyone have a clue. We are trying to find parts for the motor but need to know how big first.