On mine, the pins bolt into holes already in the flat, front part of the fender, between the drip rail and radiator. My pins are a whopping 1/2" diameter. My hood was off a 72, and the holes were there but much smaller.

If you have the holes in the fender, you can install teh pins, then dab paint on them and make a transfer to the underside of hood to locate them that way.

If you need, I can measure mine, and photo.
Steve