Significantly, there is also Montale in English, the Preface to which contains this lament by the editor, Harry Thomas:
In the end I have decided to include the work of fixty-six translators, but I might have included that of dozens more. The one real regret I have, though, is the absence from this anthology of several translations Henry Reed's rendering of the great Mottetti, for instance which repose unprintably in archives.
Thomas is referring to Reed translating into English a series of love song-poems (motets), by the Italian poet Eugenio Montale who, in 1975, was awarded the Nobel Prize for Literature.
In his Introduction to the Collected Poems, Stallworthy mentions Reed having "drafted and all but finished polishing" his translation of Montale's Mottetti, but the work never reached publication, and must still be among his papers and notebooks at the University of Birmingham.