You never change an offense or defense before a bowl game. ...
"Never" might be a bit strong. Often teams put in a wrinkle or two for a bowl, but I once saw a team come out for a bowl with an entirely new offense. That was the January 1, 1973 Orange Bowl, where Tom Osborne came up with an entirely new offense for the bowl, and totally confused Notre Dame. He moved his running back to the wing back spot, and his wingback (Johnny Rodgers) to the running back spot. Some plays were the same, but seemed different because very different people were running them, while other plays were entirely new.
The next season, the offense went back to the the normal offense, but some vestiges of the "orange bowl offense" continued to be a part of his offense for many years.