Jiffer,
Yes you can do the century!
I did in 2006 with the Rain, Hail, sleet and snow.
Most of the nastiest climbing is at about mile 90. You've got a false flat on Foxen Canyon out of Santa Maria, and then you've got on long and steep one, followed by the "wall" on Ballard Canyon. It where Versus was filming the ATOC on Friday with the big hair guy.
I was going to do it this year, but decided I need to pay bills and get my 'bent legs