1965 - 1966 Bolt Head Marking ID for Cylinder Head to Firewall Ground

[Silver Bullitt]

I've pulled and saved these three bolts over the years from different unmolested standard bore 65-66 289 HiPo engines, on the rear of the passenger side cylinder head, used to secure the grounding wire. I never marked what date engines I pulled them from, hindsight is better than foresight.

Left bolt: Swirl pattern on head
Middle bolt: "L" with slightly visible round swirl marks in background
Right bolt: "L" without a visible swirl in background.

Do they all look to be original to location?

Which of the three would be considered correct for a mid-July 289 HiPo assembled engine?

What year/months roughly would each be correct for?