Howdy Stangman:
It seems to me that you have two issues; a sputtering engine & an engine that may need to be rebuilt. My advice is to solve the sputtering condition first, then assess the engine rebuild needs.
A '67 Mustang 200 should have a Autolite 1100 carb, either for a standard trans or an Auto trans- they are different. These are very simple carbs- easy to work on, but somewhat fragile and easily susceptible to dirt and crud. It sounds like your "sputtering" problem began when you replaced the carb. That's a big clue. Do you still have the original carb? If you do compare it to the replacement carb to insure that they are the same in every detail.
If you still have the original carb and it is in good, rebuildable shape- no warpage, no threads stripped, tight throttle shaft, consider rebuilding it yourself. A rebuild kit is cheap and the directions are complete and easy to follow.
Buying another rebuild carb is no gaurentee that you will get a good one. Many times the rebuilt carb is not even the right on for your application. Float settings can be off and screws loose, and the inside dirty. At least know what you have and that the rebuild is identical in every detail.
While solving the carb problem(s) check over the ignition to make sure it is working as it should.
Once the engine is running as best as possible, begin assessing your rebuild needs with a cylinder compression test. If all cylinders are low consider whether it is due to worn rings or poor valve seal or both. Worn rings require a block rebuild, poor valve seal requires an upper end rebuild or a valve job.
If you are going to do any rebuilding start by checking with your areas machine shops on prices and attitude toward doing a Ford six. Finding the right machinist is critical. Once you've determined your direction your machinist may be the best source for the right parts.
I hope this will get you started. Take it one thing at a time and have a plan. But most of all, enjoy the journey.
Adios, David
