I did the Hertz Mustang thing last year, from SFO down Highway 1 to LA, then across to Vegas and dropped it off there. The 2005MY Mustang is a huge improvement over the earlier ones, but if you're really after a classic then you might find it hard to find a one way rental.

If you need somewhere to stay about halfway down Highway 1 I can recommend the Ragged Point Inn, especially if you're with your significant other (get a Tier 4 room - cliff edge, second floor, jacuzzi and balcony).

Rob