Supercharged or stroked 340

Ahh, you're in NZ.
What kind of octane is available for gasoline?
Typically you would run large CC chambers with boost, to drop the CR.
The Victor heads are great but keep in mind, the blower will push the air thru any port obstruction in the RPM heads..
The Victors are serious heads but I'd still consider not using them for your boosted application.
The custom pistons and headers that are required going that route is gonna add serious money......
What's the intended use? Full out track or street strip?
StrokerSul has a nice cast blower manifold.