Forever ago i used to pulled covers at a You-Pull yards years ago looking for adjustable rockers and X,J heads. I had severable sets of various covers and were at dads place. These look 283-318? But what year?
The original posters are standard 2bbl 273
What makes the early is the area at the breather/PCV is not domed up, this is true with both the standard and the Commando.