Unless things have changed - you can get assembled heads from various shops - but not from Engine Quest. Out of the box they are only bare castings. They were designed to be a service replacement for cracked but operational factory heads where you would just re-use everything.
So in my opinion things like flow data, and quality of parts can't really be guaranteed accross the board as these will vary with the other parts chosen.
In terms of lift - .600 at the valve, with a 1.6 Magnum type rocker, is limited. That only leaves you actual cam lobe size of .385" or so. They are limited because they don't have deep enough spring seats to cut down and get a taller installed height. Factory rockers don't work wel with taller valves which means a more expensive rocker setup - one that can push the overall " on the car and ready to run" cost similar to an LA based aluminum head. So they are great for factory displacements that are destined for mild to mid-sized cam. Great head on the right engine. Great "as delivered quality. But limited when looking at larger displacements or higher rpm power levels. They are a great fit for the OP's intended use.