One thing to consider when determining if it’s worth it or not is the size of the exhaust after the cut out. Having 255 cid going through 2.5” at 6500 there would be a benefit you would think but as I said before headers with a collector extensions make more power that open headers and you actually need to tune the length of the extension so it’s not as simple as having an exit for the exhaust before going through the rest of the system.
I would approach this with building a system that will cost the least amount of power loss, probably a 3.5” system with race bullets.