Hmmm, I'm out of my league when it comes to answering a zone 8 question, since I've only ever gardened in the frozen north. One fragrant clematis I have had experience with and can definitely recommend is the sweet autumn clematis (clematis ternifolia)--it's a very vigorous vine with tiny white blossoms in the fall and smells wonderful. A quick search I just did also turned up clematis crispa, which is actually native to the southeastern US and supposed to be fragrant, so there's another possibility. Or have you considered honeysuckle or wisteria?
Thanks, Petal. They are beautiful, and versatile too. This fall I planted a summer-blooming clematis beneath a spring-blooming viburnum. I am hoping it will keep the shrub interesting through the summer.