72 tooth might not be enough, especially if you're offroading (like you've been saying). I'd go even further than that... 84 tooth. Your top end will indeed suffer, but you'll get more usable torque at lower revs. Top end won't be disappointing, it won't be as fast as before.
And with your junked governor, I'd be careful of overrevving, floating valves, and bending valves.