[rotorwrench]

There are several distinct engine types in what is commonly referred to as the 8BA family of engines. The heads changed multiple times during production of this family between 1948 and 1953 for US production (1954 for Canadian production). Different applications had different heads and accessories. The two major types are by cubic inch displacement. Most are 239 cid but there are also the 255 cid types for Mercury and special applications. They both use the same block but there are different crankshafts for them since a stroke change was used to make the 255. What fits one block fits all but the changes usually work in sets for the different applications.