Your engine might burble (with a rich mix) for a while, but the engine compression increases during break-in. A 20:1 or 32:1 mix (with your preferred oil) will provide sufficient lubrication after that. I am using an NGK BP6HS plug in my angle fire head. The 'P' stands for protrusion, the electrode is slightly extended. They seem to be readily available. I suggest not doing anything to the carburetor (except idle adjust) until any ignition or compression concerns are resolved. Then you might try raising the clip on the metering needle up a notch to lean the fuel charge. The metering needle is effective to about half throttle. After that, it's up to the main jet.