I've just glanced through the multitude of messages on this board (just enough to get creeped out by all the dead john Heacocks out there, perhaps still wandering the earth in search of final peace), but it doesn't seem there's much about the Heacocks that went from Pa to Al before the Civil War. I admit that I might just have missed that issue, or don't know the official topic of this forum, but I'm pretty sure that a lot of the Heacocks in the south originated from this doctor who went to Talledega, AL and then had a bunch more doctor sons.
The letters exchanged between the abolitionist PA brother and his wayward slaveowning AL brother debating the Civil War I believe are still housed in the Duke University archives, a fact surprisingly pointed out when I was doing a project in the library as an undergrad (one of the rare times I inhabited the stacks, I regret). I was under the impression that this philosophical and religious "rift" is the reason that our last name is pronounced differently in north and south.
Anyway, I really don't know too much of the details, though my uncle, aunt, and dad are the junior geneaologists in the family. I sent my father the link to this, so maybe he can add some info. Or I could be completely off base, in which case, "never mind."