Making progress on my restoration I recently pulled out the 5-gauge instrument cluster for my August, 1966, Dearborn, Hipo, GT Fastback. During my inspection of the piece I noticed there was a hole about the size of a pencil eraser at the bottom of the casing that holds the speedometer. So, I assumed I would need to repair this hole. I decided to pull out another spare 1966 - 5-gauge instrument cluster that I had to see if I could use the housing from this case. But low and behold it had the exact same hole punched in this area. These holes did not look like anything the factory did, but possible something a Ford dealer repair might have done if a service bulletin had been issued to add the hole maybe for vapor relief. Were these punched holes added for a reason?
The instrument cluster for my 66 hipo has an ink stamped date on the back side of Jan. 21, 1966. The extra 1966 case I referred to above had an ink stamped date of Sept. 21, 1965.