headlight trim rings for chevelle

[rspanther]

I friend of mine that plays with 64 to 67 chevelles noticed that the 67 chevelle trim rings he had has a oval hole in the side by where the spring is but some are factory notched out like what I am familiar with my 68/70 ones but now I have found some in my stash with the oval holes . I seen in the GM parts book that 64 to 70 are the same but I thought the 64 to 66 only have 2 mounting tabs where 67 to 70 have 3 . I have a NOS ring and it has the 3 tabs but has the oval hole . I am confused about what is the proper usage for the different years or is there different makers or ? This has been a little frustrating trying to figure out so any help will be greatly appreciated !! Thanks David