Howdy Gary:
There are several issues with the '81 200. Do a search on "Fairmont 200s" and "Late 200s". We've been down this road before. "MarkP" is another author search you can do. He's done a number of Fairmont type survey articles lately. He's also been quite successful in attaining the results you're looking for and very knowledgeable about the last generations of our favorite sixes. Know that your '81 has the best stock OEM head and ignition system.
The Carb on your '81 should be a Holley #1946. It was/is quite restrictive and cluttered/choked by a number of vacuum/electronic/thermostatic feedback systems. It was the last factory carb effort prior to switching to EFI. It is a complicated and unforgiving carb.
You might want to explore a Carter RBS from early 70's 250 Mustangs, Mavericks, Granadas and the Merc clones. It is slightly larger in CFM at 215, compared to the #1946's 180 cfm. You will likely need to do some adapting to maintain the stock, OEM air cleaner/intake system. Linkage and distributor vacuum should be a direct swap. You may need to get the 250 carb to manifold adaptor from the donor car- or you may get lucky on the bolt pattern. Adapting the automatic choke hot air intake will take some fabbing too. Converting to a manual choke would be the simple solution.
The RBS is a fairly simple, straight forward carb that is easy to figure out and to maintain. It may require rejetting in your application for best performance and economy, but that's fairly typical in just about any carb swap.
Know that your engine will still be suffering from retarded cam timing/via the cam gear, a very restrictive exhaust system, and a low 8.2:1 CR (low for performance, torque and economy.
Enjoy the journey.
Adios, David
