Chrysler A engine
The Chrysler A engine is a small-block V8 gasoline engine built by Chrysler with polyspherical combustion chambers. It was produced from 1956 until 1967, when it was replaced by the wedge-head LA engine. It is not related to the hemispherical-head Hemi engine of the same era.
AMC V8 engine
Bore center measurement was kept the same as the Gen-1 V8 at so that boring equipment could be reused. Other than that, this engine is vastly different from the Gen-1 model. The Gen-1 engine is physically the size of a big-block Ford or GM engine, and is sometimes called a "big-block". The Gen-2 is closer to the physical size of U.S. made small-block V8s except for the bore centers, which are the same as some big-block engines. The only parts shared between the 1966-67 Rambler V8 and 1966-91 AMV8 are the lower cam timing sprocket and the timing chain.