Max horsepower with EQ heads?

"the point is, what could be had for power out of these EQs without major expense beyond big valves and a full port?"

I still think 2.3 x the max flow will get you close given the attention to detail, gas porting, vacuum pump, etc etc etc. Leave the big block comparisons behind. We're talking a 4" stroke small block. "Major Expense" will be in the fitting of valvetrain you want (and would need) to theoretically reach your goal figures. Plus this is a race car - for that extra expense you get an extra 40-50lbs on the nose at no extra charge. As Scotty would say "You canna change the physics, Caaptain..."