I don't know where you'd find results for wrestlers from decades ago like Brands or Ironside, so it's tough to know how their wins over NCAA champs compare with Metcalf. In recent era, other top Hawkeyes don't quite match Metcalf for NCAA champs beaten.
Metcalf: (5) Schlatter, Caldwell, Jenkins,Burroughs, Molinaro
Gilman: (4) Tomasello, Garrett, Cruz, Delgado
McDonough: (3) Megaludis, Delgado, Garrett
Clark: (3) Gross, Tomasello, Delgado
Ramos: (1) Oliver (Ramos stuck behind Stieber...)
St John: (1) Dieringer (Impressive considering Dieringer ended up a 3 timer. St John stuck behind Dake and Taylor)