2.25” or 2.5” exhaust??

Hi all- was out driving the duster today, when it got loud! Pulled in the garage to look, sure enough big ol rust hole in muffler. Looking further, I’ve got holes here there and everywhere, pretty much time for new. What’s your opinion, Accurate and Waldron will provide a 2.25” system, TTI has 2.5”. I understand the straight stock setup is too small. 1970 Duster, 198 all stock currently, working on a super six manifold to go to a 2 bbl.
Thanks as always,
Tim