1971 340 Cast Iron Intake Manifold #3512100
Is a damn good 'breather'.
Just a little gasket-port matching and some smoothing of the plenum-area,
and you've got yourself one solid performing Intake Manifold.
No big deal that it weighs about {+28 lbs.} more than an Aluminum Intake.
Problem solved > You just have to find a lighter Girlfriend.