500 hp from a 69 440?

The '69 heads are most likely 906 castings with 2.08 intake and 1.74 exhaust valves. They do not have hardened seats. They are very similar to the 73 heads as they both are open chamber.Not the greatest/easiest way to get to 500hp. I would just use the 73 heads (346 castings probably, but it doesn't matter what #, they all flow about the same)and install 2.14/1.88 valves with hardened seats. It would be great if you yourself could use the MP porting templates( cheap, like $20) to port them.That's a big improvement. Then get some KB or Speed-Pro Hyper pistons.