For a more run-of-the-mill fight, enter "H074W57Z" while in Tournament mode. You'll then be fighting for the title as Ali with a number-two ranking, 40 wins, and no losses.
Harder Game
For an unusual match, enter the password "H07007Z" while in Tournament mode. You'll be fighting as Ali with a #1 ranking, no wins, and no losses. Your opponent is an elderly gentleman named Ali Mohammed. This guy looks strangely familiar, except for the white eyebrows, mustache, and clothing. Don't let appearances deceive you, he may look rickety, but he's tough as nails.