Man, your valves aren't spending much time over .500 lift
Give that baby more lift and more duration. It's a 572.

Better heads are always key to making power, but you also have to get those valves open fast and hold them open. You're probably already propped past your HP peak.

MC

Whats yours guys feelings on the Merlin III aluminum CNC 345heads? Seems like a reasonably priced upgrade as far as heads go. Stock port locations. Flow numbers look good for not having a 6" pipe (like afr does on their flow testing). I'd be going from the Iron Merlins with same port locations so I'd likely be able to go back without making changes to my CMI's or dart intake.... Some hand porting would likely take them even further if possible with these

i have a similiar bbc with afr 357's. i changed from a .632/.632 244/254 at .050 to a .690 266/268 and picked up 80hp at 5900 on the dyno. boat ran 8 mph faster.