Heads, how much gain?

I have been a long time flag waver of porting your iron heads for a more than likely cheaper cash out lay and better results than a new set of aluminum heads, which rarely come good to go.

A lot of this is based on the performance level your looking to achieve. What is it exactly your trying yo do? How fast do you want to go? And of course, where do you want to do it? Going fast at the track is far different than going fast in the street. The build changes.
And the cam, converter, rear gears etc... well, that is a big part of the build.

I've seen guys run mid 11's with OE iron heads. So going fast is possible with iron heads. BUT, the rest of the build, the way it is combo'd together is not what I would call a street friendly combo.

You do not need "High flow" aluminum heads to go fast. You need a well thought out combination.