It's interesting to me to think about this question relative to the Corvette crowd and Bloomington Gold. If you're trying to attain that level of perfection, no upgrades are acceptable (correct?). I'm in Milt's camp. Change as you wish but keep all of the original parts and don't cut the tub so that a future owner may put it back to "original" (per the Kardex?) as desired. Otherwise, go out and enjoy the darned thing! :)