Hi,
I have bred easterns from their entire range for over 20 years, including the s. GA morph which Kevin Enge and myself developed from animals that he originally collected from Echols and Tift Cos in S GA. As a general rule, southern locality easterns are larger than northern types, with s. GAs generally being the largest and NJs generally being the smallest. However there are always exceptions. In fact, a notable exception is the original wild NJ female that started my lineage (a looong time ago). She was reportedly a six footer collected by a NJ DNR guy crossing a Burlington Co. highway. While in his care, she layed 20 plus eggs. Those babies went on to found the most common line of NJ easterns, which are typically on the smallish size. Adults that I have bred and raised, even 5 generations later, seem to max out at 40-48 inches or so.
As far a GAs are concerned, well cared for adults are usually 5-6 feet for males, and 4.5-5 feet for females. All of the adults that I have bred and raised have fallen within this range, although I have heard of smaller adults from the same lineage in other collections.
Healthy eastern kings from any locality have a savage feeding response, which can be mistaken for aggression. If they are well fed, are hooked out of the cage, and you don't smell like a snake or rodent, they tend to calm and curious, but I have often made the mistake of handling an eastern after other snakes and have chewed on.
Good luck, and an eastern from any range makes a great addition.
Will