The Ford C4 was a three-speed, medium-duty automatic transmission introduced in the 1964 model year and produced through 1986.
It featured an aluminum alloy three-piece case (bell housing, main case, and tailhousing). This was significantly lighter than earlier cast iron Cruise-O-Matic designs. It also used a Simpson planetary gearset.
It was used with Ford's inline six-cylinder engines and small V8 engines (see Ford Windsor engines), usually up to 302 in³ (5.0 L). By comparison, the 351 Windsor and 351 Cleveland small and intermediate-block engines were backed by the medium-duty FMX. A few C4s were built with a big-block bellhousing to use with Ford 335 engines, notably the 351M, but these are very rare.
Cruise-O-Matic was just the type of Automatic Transmission that the C4 and others were called. The Cruise-O-Matic was first introduced in 1958 and Ford quit using them in 1980. Long Before the C4, There was the FORD-O-MATIC Auto transmission... There were even C6 Trannies called Cruise-O-Matic as well.. The early '64 thru '66 Trannies were called "green dot" trannies. In 1967, They beefed up the C4 and changed the gear selection with two gears reversed, but you can still swap a '67 tranny into a '66 and earlier car.
The bellhousings of the trannies have different bolt patterns as well. The 64/65 has a 5 bolt pattern, and the late 65-'66 and after has a 6 bolt pattern on the C4 bellhousing.
To swap it out you must match the bellhousing to the block.
Right: big block + removable bellhousing = FX/MX/FMX family of transmissions which are commonly called cruisomatics. Small block + removable bellhousing = C4. Any engine + One piece trans body = C6. This link may help.