From THE 1949-50-51 Book: "...Contained in the serial number is the Engine type, Model year, Plant which assembled the car (1950/51 only) and the numerical sequence of assembly." So, what you have is "O"=1950 and "MP"= Memphis. There should be an "H" or "B" prior to OMP which would indicate a six)H) or an eight(B) cylinder engine;ie., BOMP. Hope this helps. Ken