As a Hobartian I'll be the first to admit. Nice empty country roads are hard to come across down here.
I'd stay up north.
I personally love the west coast. I really enjoyed the road from Devonport to Queenstown via Middlesex then to Hobart. That was a good one. Many Caravans in the summer though
I'd have a crack at pulling the head off and changing the headgasket without machining it, if it works, hurray! if not, meh, what's a head gasket and a few hours of your life worth?