The 200 in any form at their current age needs a rebuild. The later 442, MC SS and GN/GNX units had a couple steps up on the rest of them, but for the price of the servo, valve body , one other part that is slipping my mind at the moment, the price to rebuild and upgrade those parts is minimal to say the least. They are worth money as the cores become fewer. And the upgraded parts aren't as popular as they once were, but all of those parts can be found at reasonable prices.
Good luck with the 307 though.