Turning over the 5418, we noticed only one prominent difference, which was the size and shape of the heat crossover passage in the center of the manifold. The new one has some casting details, most noticeably some stampings, including a circular logo at the front. Look for that at the swap meet in 30-40 years to determine whether it’s an original or a 21st century reissue. A similar intake (PN 5419) is for use with four-bolt Rochester 2GC carbs. A third version (PN 5417) fits small-blocks with Vortec cylinder heads.