A reliable, 700hp first project is a pretty good start

How much HP a turbo is capable of is only 1 aspect of sizing it. If we were to plot Randy's engine on a map it would probably push off the map to the right and low (as mine does). Most big blocks will push off both a compressor and turbine map hard to the right and low. That turbo might be capable of 600hp, but to do that it's expecting a 3:1 pressure ratio at 1/2 the lbs/min that Randy is pushing through it.