In my hunt for much earlier DF wheels (car built 01C) I found many March dated wheels around the valve stem. Your hunt will be much easier due to having a spring buiilt car! In reference to your question concerning the have or have not date code, it depends on when the car was built as the early part of the 68 production run were using large font DF wheels un-dated around the valve stem. The earliest dated valve stem DF wheel I have seen was a Dec., 67 wheel, yet I have center sections dated 12/67 with the large DF font and no date code around valve stem.
