Nope, you probably need to rebuild the tank with a new bottom. IMO the value of your time to do this correctly would far outweigh the cost of just buying a new tank.
Bummer.
Edit, adding;
Are you sure it's cracked? Aqueon 65G tanks are supposed to have tempered bottoms, which if scratched would shatter. Could it be a little line of silicone slop or something like that?