Given your rollerized valvetrain, the reality is that any quality oil of SAE 30 viscosity and decent HTHS that is shear stable will provide all the protection you need. The clearances (which are determined from other factors) will then determine whether you need to increase/decrease the viscosity from this starting point. Synthetics (including group III) provide additional high temperature insurance for a variety of synergistic reasons. A good engine builder should ASK YOU what viscosity oil you would like to use and then build the engine for it. OR, if you haven't a clue, he should build the engine and then TELL YOU what viscosity oil to use. In any event, accurate oil temp and pressure gauges (along with professional UOAs) will allow you to optimize your choice given the peculiarities of your engine and the environment you operate in.
How high of quality oil do you need? Well I've seen numerous Corvettes tracked all season long on nothing more than M1 10w30. The key is they keep their oil temps in check with a good oil cooler.
