I got the impression that you would stick with the alcohol fuel if you were converting a glow engine to spark ignition.

You can always run without nitro, and mix your own methanol and oil. It'll be a bit harder to start and mixture is more critical without nitro, but that's the way a petrol engine would be anyway.

You would have to modify the carb to run on petrol, and the power output would be around 20% lower, compared to using methanol.