I'm not a loph expert, but most of those look like they come from the diffusa group to me. There are 3 in there that have well defined ribs that could be willies though. check this out:
http://www.kadasgarden.com/Lophophorachart.html#comp
ps I've never seen anyone do a definitive test on alk profiles of grafted vs non grafted plants, and everyone I've talked to who ate a grafted plant said it was not lacking... "grafting = little alks" could be totally wrong as far as I know. that statement reeks of infinitely propagated internet speculation.
EDIT forgot: nice find btw... what did the grower say about their ID???