Those are Magnum heads. There are some really nice builds using those heads on the 318. In stock form they flow more air than any of the earlier small block heads except for the W2 heads. The key to making them work on the earlier LA small blocks is that you need to use lifters that have through oiling (AMC lifters) as they use an oiling setup similar to the small block Chevy where the oil supply to the heads and rockers is through the pushrods and not through the deck to the rocker shafts like early LA's. They also have an intake mounting configuration that is unique to the Magnums so early manifolds aren't going work unless you do some mods.
BSE Racing Engines