Ford casting numbers are located in the head of the engine and act as serial numbers for the type of motor to which it mounts. For example, C8ZZ-A is a casting number for a head used on the 1965 Ford Mustang 289 engine.
There are hundreds of different types of casting numbers produced by Ford. Each number includes a variation of one or more blocks. The 289 Windsor engine, for example, has several different types of casting numbers for its heads. Each casting number differs in the year of its production and application. Some 289 engines were used in older model Ford Mustangs, while others were used in Mercury Comets.