This new database is on trial at the University of Sydney Library until mid-June (sadly only available to staff and students). It includes scans of many classic titles, such as American Splendour, and some lesser-known curiosities from the underground comic scene of the late 60s and early 70s, such as the charmingly-titled Bum Wad (1 issue, 1971, sample strip, 'The Regurgitate Raga'). From the 80s, there is an almost complete run of Flaming Carrot Comics, a title I remember being bemused by in a fusty comic shop in Liverpool c. 1984 when I came across it as I rummaged around for books by Cordwainer Smith.
The database is probably available via your local college / university too. If it's not, you're at the wrong institution.