Howdy '83fairmontI6:
Yes, the '66 manifold will fit your '83 200. Know that it will not mount up with your smog and EPA stuff which may put you at odds with the government.
Some vehicles in the '79 to '83 era used and odd exhaust manifold with a cat attached directly to it and another cat farther down stream. The 1st was a fast light type, an made for a very odd, low performance exhaust system. Check with yur local and federal law requirements before you change it. But the '66 is a cleaner, and a freer flowing version.
Adios, David