I think it's all a matter of personal taste. You can easily sink $4,000 in any Z for repairs and upgrades. I've seen some extremely nice Z's in that price range. If I had a budget to pay $4,000 up front, I'd hold out for a 70-72. If you like that 260, and prefer an automatic tranny, then you'd be hard pressed to find one in that condition.
Just throwing in my two cents...