Evaluating Surface Defects of Green Sand Cast Ductile

I am looking for a rating, grading, or scoring system used by foundries to rate green sand cast ductile iron surface defects, such as porosity, dints, dings, gating. I am trying to provide a standard that our sales, engineering can communicate on the same page. I have talked to some of the foundries that we use and they state an improvement in the casts will be a higher grade or rating and will cost more. My problem is that the foundries will not provide the standard to what they are grading to. I have spent time searching the internet to no avail. Our sales is pushing for the best quality blemish free cast for our customers. Engineering is not concerned with cosmetic issues and is only concerned with fit, form and function. Is there a standard that evaluates surface defects of green sand cast ductile iron?