I've gone on reccord before stating that I do not care for Z-turn tractors. They are too awkward to use IMO. What you need Ken is a John Deere 400 series or X series with four wheel steering (the X series replaced the 400's a few years ago). My parents have a 445 (kawasaki fuel injected engine) with four wheel steering, and you can really cook on those things. I have the 455 (inline 3 diesels) with the two wheel steer, it doesnt cut as fast because of turns, but its got more implement options, which I'm all about. None of these models are cheap, but they will last you for at least 20 years.
http://www.deere.com/en_US/ProductCa...m=ho&link=dnav