Jeff, great to hear back so soon on this issue. So from what you are saying, the dimpled hood vs. non-dimpled hood cannot be pinned down to a specific manufacture date period.
Regarding the '66 Shelby all steel hood, I understood that this was not available on the '65 cars. And I have heard many a discussion on how many all steel hoods were created in '66, and at this point, all that I can gather is that there were fewer numbers of the all steel hoods as compared to steel lined for 1966 Shelbys.