Big horsepower 318 builds

I don't know much about Speedmaster heads....are they USA produced or Chinese?

When you buy an Edelbrock head, you are buying the head but also the degree of confidence in their manufacturing and the R&D that went into the head. It doesn't matter if a head makes 3 percent more power if it has porosity issues or loses a valve seat after a couple years.
Speedmaster head thread index