Eagle has got big stroker cranks for 360 / 5.9!

Icetech said
So.. i am curious.. for a street car that wants a nice power curve and not max rpm/hp how much do smaller heads hold you back below like 6000rpm?

Cid would play a huge role

Icetech said
i'm talking like 280@.500 vs. 310ish@.500?

Somewhat hard to say, If the 280 had the right port volume and shape to turn the Cid and make power at 6000 rpms but the 310 didn't than the 310 would peak lower in rpm and probably hp.

But let's say the 310 turned more rpm and made more peak power probably would make more power at lower rpms too, just a narrowed gain to even a slight loss as rpm goes down.

Icetech said
Does the extra flow come more into play at a higher rpm?

The air flow demand is gonna go up as rpm does, 6000 rpms needs about twice as much airflow as 3000 rpms, above peak torque your engines VE% (ability to fill cylinders goes down as rpms rises) so less torque, why hp still goes up after peak torque is cause of the multiplying effect of rpm, hp % of torque. About 1000-2000 rpm higher than peak torque, torque drops off enough around 90% of peak torque where the drop off is faster than the rise of the multiplying effect of rpm. Eg.. Hp is 100% of torque at 5252 rpm and 125% at 6565 rpm.

So above peak torque your engine finds it harder and harder to fill the cylinders.