got to question the wrench needed to tighten those '5/16' bolts. If its a 9/16 hex then they are 3/8 bolts. 5/16 take a 1/2 wrench as those head angles are 3/8 for sure. Whats head casting number
That's where I was going, later heads on earlier engine, or later engine and heads, with earlier intake. The bolts look larger to me too, but there is no perspective.
