By any chance do you have the test pipe part number?No problem replacing it with a piece of 3 1/2" pipe. Ford used to sell a "test pipe" that would bolt right up. All you needed to do was to cut it to length bolt up one side and clamp the other.
I have had one on my truck for over 100,000 miles.
However if you are in a area that has emission testing the n the cat needs to go back on to pass those inspections if they do a visual.