things you can do to improve power on the 200;
1: if you havent already swap out the load-o-matic dist for a later model duraspark dist, and hook it to a chrysler ignition box and msd blaster 3 coil. i have done this already on my 66 falcon and it works great. engine lights off first time even on a cold morning(below 30 degrees) with NO choke and only two pumps of the throttle.
2: add a weber or autolite 2100 2bbl carb, or the offenhauser 3x1bbl conversion.
3: you can add a larger cam. classicinlines.com has a selection of clay smith ground cams that work real nice.
4: add a dual outlet header and dual exhaust. this is where you will pick a decent amount of power(after the cam swap) as the stock exhaust leaves much to be desired.
5: add a T5 and 3.55 gears.
these mods will really wake up your six, and you will likely surprise a few V8's in the process.