C7DF-R

So the C7DF-R origannly would have come off of a 1967 Falcon eith the 289, but because the mustang shared parts with the falcon line would have also been applicable to the mustang line, so should be no problems there. The carb should be perfect for your application.

The bogging down on acceleration does sound like she is running a bit rich, you didn't say what jetting you have or what accelerator pump setting or bench setting you have.
I would go back out and bench set the carburetor for a 1967 falcon with the 289, thats the float settings, both choke settings and check the jetting to make sure it is correct for the 67 falcon. then readjust your idle rpm, and high speed idle rpm and then the idle mixture screw. If at all possible use a vacuum gauge and the RPM gauge when doing the idle mixture screws. You want the highest RPM with the highest vacuum, and you will have to do it several times while adjusting your idle RPMs.

But the bad news is I don't believe that it is running rich enough to cause your carbon buildup. You have not mentioned any black smoke, which is what I would think you would have getting carbon buildup after only 30 minutes of running.
I would look very seriously at your ignition system. Sounds to me like you are getting a very weak to little spark. Or perhaps you are using the wrong type of spark plug. I know there are a lot of stuff out there nowadays but those good old autolites still run with the best and don't cost you an arm and a leg. If you are still getting problems play with the heat range. Go one range warmer and see if that helps.

Bill White
White Automotive