hey guys, i'd really like to know what would work out the best here... in order to install my JDM 4-1 DC header i need a shorter cat... so i'd like to know which option should fit best on my 2¼ DC Cat back...

Car sound Hi flow cat.. if i buy both flanges, i should be able to customize it?

JDM cat 2½ header flange with a 2¼ modified exhaust flange

Or smsp test pipe that is 2½" and try and fit it on my 2¼ exhaust by changing the exhaust flange?

let me know what you would do if you were me... thanks...