All the reproduction Zinc Plated Necks come without the factory "vent dent" in the face that allows your gas tank to breathe with a non-vented gas cap (which all O.E.'65-70 Mustang Caps were). All the reproduction Painted / Powder Coated necks come with this dent as do the '65-66 & '67-68 Conversion Necks, it is just the '65-69 Scott Drake and CJPP Zinc Plated Necks that come without. Anyway, I started adding this dent on all these necks a while ago, and finally finished a write up on the subject. See attached PDF.
Doug
ADDING VENT DENT.pdf