I recently found this online magasine in the US. There's some nice summary articles on the S1,II,and III plus a historical context on Italy at the time and some racing recolections of a US driver with a couple of Zagatos.
http://www.velocetoday.com/At the risk of stating the obvious - also some bits on the Dutch Viva Lancia site, in particular on the Dagrada.
http://www.viva-lancia.com/Something of a surprise was finding a list of Formula Juniors and many more list the Appia engine than I knew of, including Cooper. On the "page one" follow links to pages 2 and 3. The only ones I knew of were the Dragda and Volpini.
http://www.formula2.net/FJ_Cars1.htmDavid