The non-selective version of the Fox-Kautzky trigger was only offered by Savage, and then only in 1933 and 1934. The non-selective trigger was a $10 option while the selective was $23, fitted to any Fox gun old or new.

In over forty years of looking at things Fox, I've never seen a drawing or cut-away that shows that trigger. You are likely all on your own on this one.