The "A" in the third position of the engineering number prefix is "Generic Ford". It is not make/model specific. In other words, all of those EnAE-6059-xx timing chain covers were originally engineered for a generic 198n Ford. Then they were used on many models for as long as they were needed until a need arose to redesign them.
E3xx could have been superseded by a redesigned E5xx cover of they could be for two different applications. E5xx could have been superseded by a redesigned E8xx cover or they could be for two different applications.