I spent pretty well all day yesterday on the computer, surfing the net, Facebook, anything I could think of, (wandered out for tea at 6 o'clock and She Who Must Be Obeyed said "What have you been doing all day?"
"Well...nothing really..." and got the 'raised eyebrows' look,) and I think I may have cracked it.

I found this site: http://billingsok.swiftsite.com/ and wrote to them asking if they could help.

And...(drum roll please,) got this reply: 'Several of the names you have are cousins of mine .Still some of them live in Billings ,Oklahoma, Such as Karen Durkee. Marilyn Durkee lives in my town, Perry, Oklahoma. That was a great group of children. hope the ones riding it now are as good. Shirley Holt Self'

So I have written back asking if she would be so kind as to send me some contact details for these people.

Fingers crossed!