It looks like a 29K4, right? Be happy its running well because many of the parts, especially the drive rail are entirely unavailable. It would cost $250 to have a new one machined if yours breaks. Unlike the 29K50 + series, most of the generally available drive parts are not interchangeable. The 29K4 was very popular in its day and its quite remarkable yours still runs. Its really old.
That said, $450 isn't a bad price. Pack the head up really well if you ship it. Good luck with that!