ACT 8 is not directly supported.
Avaya points to a third party vendor:
Optional Microsoft Outlook 2000/2003/XP, ACT! 6, ACT! 7.0, Maximizer 8.0 and Goldmine 6.7 for contact management integration. ACT! 7.0 and higher is supported via the optional TAPI.NET available from CRM Addons (www.crmaddons.com) a third-party vendor.