Found the answer
You seriously can't measure it with a ruler? That is how I measure them.
Ford Mustang 3.7L V6 Engine Explained | A 3.7L V6 Mustang Owner Resource for Modifications and Repairs
Says it's fitted with a 68mm TB.
Of course, but I finished late and had it all together connected with an Airaid cold intake and didn’t want to have to undo it again. I wanted to order the correct rubber reducer, that’s it. You didn’t need to reply. I thought getting a quick answer here was quicker than taking it apart.