Any good quality fuel should be okay for breaking in an engine. I suggest using the same fuel you intend to run after it's broken in. If you're not racing, don't bother with 30% nitro. I used Sidewinder 20% in my rigs and have heard good things about Byron's and O'Donnell's.
break the engine in on whatever fuel you are going to be running through it. Preferably a fuel you can get locally.
If you can get O'donnell, wildcat or trinity monster fuel in your area, those are good, consistant fuels that you wont have to change the carb settings after every quart/gallon. O'Donnell is my personal favorite