What carbs are you using and what condition are they in?

This manifold is a lot less difficult to make work (and make the same power and torque) as the Weiand and offers more hood clearance.
Back in the mid 70’s Chrysler ran them both on the Keith Black dyno and we’re very close close in power. Politics ended up making the Weiand the manifold of choice on the few factory cars in SS.