TH350 - You'll need to find 1969 brackets and linkage for the kickdown cable that does not exist on other transmissions. Alternatively, you can fabricate the bracket and throttle arm if you have to. Shiftworks has a kit for your shifter.
200-4R - You'll have to fabricate a bracket and throttle arm for the TV cable and you'll have to buy or devise a means of electrically controlling the lockup torque converter. You'll also have to use a TH400 crossmember that bolts to the subframe in the same place as the ST300 crossmember but it bolts to the transmission further back in the car. Shiftworks has a kit for this one too.
In my opinion your ring & pinion is too high for the overdrive 4th in the 200-4R. Will you be running in 4th gear below the torque band of your engine? Try riding your bicycle uphill in 21st gear.
