As far as exhaust valves, the higher the compression the smaller the exhaust valve can be. Example- B1 2.30 intake 1.78 exhaust. I run those sizes in my 440-1 heads. Unfortunately i found out they made the same power as 2.25/1.81 sizes. So with that being said, a 413 block that will safely go to 4.250 or 4.280 could make good power , and if the block is cheap to buy or already owned, that will offset some of the piston costs. Also how good is the main webbing on these blocks? If it is better than a 440 that is another BIG point in its' favor if you plan on making a lot of power.
