okay, so I answered one of my own questions. this is what appears to be the top-20 all-time after yesterday's race.
66:57 Kara Goucher, (downhill, Great North Run) 30 Sep 2007
67:25 Molly Huddle, Houston 14 Jan 2018
67:34 Deena Kastor, Berlin 2 Apr 2006
67:41 Molly Huddle, New York 20 Mar 2016
67:53 Deena Kastor, Philadelphia 18 Sep 2005
67:55 Jordan Hasay, Prague 1 Apr 2017
68:05 Kara Goucher, Chicago 2 Aug 2009
68:19 Molly Huddle, New York 19 Mar 2017
68:21 Emily Sisson, New York 19 Mar 2017
68:23 Joan Benoit, Boston 18 Apr 1983
68:27 Amy Cragg, Marugame 5 Feb 2017
68:38 Jordan Hasay, Houston 14 Jan 2018
68:30 Kara Goucher. Lisbon 22 Mar 2009
68:31 Shalane Flanagan, New Orleans 24 Feb 2013
68:31 Molly Huddle, New York 16 Mar 2015
68:34 Joan Benoit, Philadelphia 16 Sep 1984
68:36 Shalane Flanagan, Philadelphia 19 Sep 2010
68:40 Jordan Hasay, Houston 15 Jan 2017
68:52 Shalane Flanagan, Lisbon 25 Mar 2012
69:03 Kara Goucher, New York 20 Mar 2011
amendments and additions welcome.
Cheers.