Really? It's 400 plus inches. It needs a 1.875 tube about 30 inches long and the cam to match it. That 1.625 tube is for dead stock stuff or Comp eliminator. There really is no in between.
Just my experience on our dyno testing small block headers on a 423.5 ci LA engine to 6,500 rpm. I realize it wasn't much of an engine as it only made 601 HP on 91 octane.