There's so many variables, there really can't be a hard number in my opinion. In an offshore marine application you have almost unlimited cooling capacity, so I can't really see an edge there for or against, as long as your combination and tune up is good. It's true the alu head may give you a little extra safety factor (much like forged pistons) if your tune up is off, or your combo really needs a bit more octane. Chamber softening, polishing, etc, on an iron head can help mitigate pre-ignition as well. I have some iron headed boosted stuff in the 1000-1100hp range that has run for years with no issues, and am currently doing a pair of 540's with iron RHS 320's with 4.0 whipples, and a 540 3.3whip with the eq320's. Also some marine race stuff that requires a 23 degree iron head and makes 1.8hp per cube. I don't tune it any different because of the head material; chamber and piston design have far more influence.

I think the main advantages of aluminum heads, as has been previously stated is : Wider selection of port sizes and shapes, weight, and repairability after catastrophic chit. If you can find an iron head that fits your engine design criteria, and the durability and corrosion resistance is a benefit, then I wouldn't let a theoretical hp limit enter the decision process

Conventional head I'd say it's equivalent to aluminum. The material of the cylinder head is not it's limiting factor. The availability of a comparable head to it's aluminum counterpart is going to be the limiting factor. Since we're talking predominantly about BB Chevy, the RHS 360 can be ported and valved to make stupid power on a really big engine. Same with the 345 Iron Eagle. Engine builders and cyl heard porters will have their preferences. Like I said before, there are racing sanctions who's rules dictate iron-only and there is NO shortage of power in those classes. I have a customer/friend who has a 509ci BB Ford in a truck pull class that demands iron heads. He runs the IDT head and the engine turns 9800 rpm and makes over 2hp/ci with a 4150 carb n/a. That head would be right at home in any other application; blown, bigger cubes, marine, off road, whatever. It's basically a copy of the A460 head only made of iron. There are comparable BB Chev builds with iron heads too. Unfortunately RHS quit making that head.

Do you have an A/F ratio or BSFC range that you like to tune for (blown)?

Using bsfc numbers as a tuning method would scare me.

power-adder and aggressive tune-ups?

"I took my silverado to the dealer and they gave it an aggressive tune-up because it had a power adder K&N filter..."

Was getting some PM's about the EQ heads. Heres a couple pics of them as requested

Spec sheet

Those look like very nice castings.

Mild do you think the hard anodized will hold up in salt?

Does hard anodizing work on cast iron ? If so, best hard anodizing I've seen was how Canfield used to do there aluminum heads. They would hard anodize everything but spark plug threads/seat , valve seat, and accessory bolt holes. Yes, the deck suface was anodized too. Since anodizing makes normal grounding points dead, run a negative battery cable to both heads. Again, with accessory holes and spark plug threads/seats bare, your ignition system will work as desgined. Coolant temp sensor will have to be grounded externally (easy - just ground the body of it) and if you have electric choke, the ground wire will have to go to one of your new ground points. Oh, get the intake manifold hard anodized too - especially if aluminum.