Advice on 440 into 74 Duster exhaust

I understand now. For an almost stock engine I don't feel that the manifolds give up too much power. If Shumacher does have Tri-Ys I would personally rather use those instead but that is all up in the air right now. As far as the value of the HP manifold, I'm concerned less about that then fitment and the potential headache of replacing headers every 5-6 years (if there is even any gasoline by then)