[bigblockv6]

Steve, you won't have to use the 305 heads, even though the 305 manifolds have small ports they will work with the Magnum heads. I bought a 478M that was a new replacement engine in a 63 Tilt cab that had the original small port intake and exhaust manifolds that came in the truck. If I were you I would start searching for the correct manifolds, someone will have what you need, meanwhile if you'll be running the small port intake a Holley 500 will simply bolt on with an adapter.