My heart sank today when, in the course of mapping out changing motor mounts, I was able to clean the area that has the production date cast onto it for my supposed "68" 318 as was described by the seller. 1-10-73 is just a bit off from 1968. There goes my extra compression point. I suppose with early 273 heads, it wouldn't have mattered much. Just chaps my back side for not checking to begin with.