When they say 2 1/4 or 2 1/2 inlet or outlet, they are referring to inside diameter. If you were to swedge the tailpipe over the outlet, it would be a very odd size, and you'd have trouble finding a clamp to fit. Your guy probably left the front pipe a little long, then had to shove the tailpipe in too far to clear the axle. It's going to take some heat and muscle to get it apart and straighten it out. Good luck