I see Harry being good enough to take Foreman in to at least the 6 th . By then though Foreman is ready to destroy Wills.
You can schedule it for 12, 20 or 50 rounds if you like, not sure if it would make a much of a difference. Wills was a great fighter, make no mistake but I don't see him making it past the mid rounds against George. He would likely give a good account of himself and show flashes of boxing savvy before the show's over. And the show would be over by the 5th with more certainty than Bricktop can provide.