...using the old panel to make a template from...
I have been working with two different 67 hoods lately, my original date stamped October-'66 hood and a date stamped April-'67 hood, both with the original pin letters.
Curiosity led me to try to make a couple of templates, if for no other reason, to have on hand if ever a need should arise. I cut two strips of sheet metal 12 inches by 2-1/2 inches, one for each side of the hood. The April dated hood was beat up a bit so I used it as a "donor" to build the template from. I first cut out the back side hood reinforcement metal, clamped to the top of the hood, one of these strips... centered over the pin letter holes & aligned with the leading edge of the hood. Drilling from the underside of the hood through the template sheet metal. This gave me an accurate template to do a few test "drillings" on some scrap sheet metal. I have now tested the template and it worked perfectly, even allowing for the barrel nuts.
Another situation peaked my curiosity. I wondered how well these two different hoods matched up to each other in the letter spacing.
First, I measured each hole spacing from the center of the hood and the leading edge of the hood....Basically, they were identical. Then I placed the template over my October dated hood and the pin letters actually inserted THROUGH the template, right into the hood! 100% identical spacing within a .001"! Amazing! Now, the leading edge was ever so slightly off but less than 1/8" BUT
the donor hood had been repaired on the leading edge so this would have changed it slightly.
100% sure now these were definitely all punched out using the same machine from the factory, there in no other possible way these holes could be THAT close to identical some 6 months apart on the production line.
The BEST way I believe a restorer could be to "as close to original" would be to section out the old panel with holes and simply use the original panel as your template. Obviously, once that original panel is gone, probably what I did above is your next best way (copy from another example). ONLY metal templates will help to keep your drill bit from walking around so other ideas might get your spacing correct but I doubt you can stay on track and have them look as consistantly good as the factory did.