Urban dictionary:
http://www.urbandictionary.com/define.php?term=hilljack
I would say that the first definition is the generally accepted 'correct' one in Ohio. Hillbillies are to the south of the Mason-Dixon Line, Hilljacks are in the north.
I think your questioning what a hilljack actually is proves that the term is almost exclusively used in the Midwest, and that Texans, therefore, cannot be hilljacks.
It's like one of those SAT questions:
If all West Virginians are hilljacks, and some hilljacks are hillbillies, are all West Virginians hillbillies?