Engine Pro's Help please

It's a phenominal amount of money for what you get, and I seriously doubt they are capable of 600hp on a street engine, or many race engines. I'd like to see someone like Modern Cylinder Head or Porter flow those heads. I'm not positive how they do it, but the shop I use can build EQs using shelf part number Chevy valves (longer) and they use a Chevy rocker design for mush less that is "perfect" in terms of geometry and runs up to 7K rpm on the modified tour cars for about $5 more than FBOs "Stock type" setup, and that's including stainless performance valves and matching retainers and locks that FBO wants more cash for. I was quoted $1K to do it. I've seen them on the dyno making 460+hp out of 360s with a NASCAR spec 2bbl Holley and custom hydraulic cam. That dyno test was the whole reason I started looking at EQ heads in the first place, and they were doing them 2 years ago.