Does not appear to be a style that was generally found on the 1st gen hood insulation, all of us and all the cars we have seen. I don't recognize them, certainly cars get serviced, painted or modified and aftermarket retainers 'could' have been sourced during the life of this particular car. Could be a Ford, AMC product or Mopar or aftermarket decades old Au-Ve-Co, Dorman etc. They look sturdy and w/ steel construction. A internet image search really did not turn this style as a return. Not saying they have not been on this car as a recent add (*Looks Old) but while they look familiar, just not what has generally been accepted as original or stock restoration parts.
The 1968 AIM list the retainer under the L48 section A4, Part item 9 PN 3909199. The graphic drawing show a circle style
