One final route on my list today was the 9 mile Old Creek Road from CA 46 south to CA 1 near Cayucos. I've never had been down this one before it came recommended from a couple friends who frequent the area:
https://flic.kr/s/aHskWhtkY3
SOOOooo....cool road but it ain't Santa Rosa Creek Road, really this can't quite compete with the heavy motorcycle traffic and lack of historic value that Santa Rosa being the alignment of both CA 41/46 at one time. The first five miles have a heavy drop from about 1,300 feet above elevation to about 220 above the Whale Rock Reservoir. Its obvious the route is very popular because there is a crap ton of safety measures like directional signage and bumps in the center stripe. Apparently the Whale Rock Reservoir was completed back in 1961 on Old Creek but Old Creek Road was under San Luis Obispo County maintenance even back in 1934;
http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~247349~5515385:San-Luis-Obisbo-?sort=Pub_List_No_InitialSort%2CPub_Date%2CPub_List_No%2CSeries_No&qvq=q:california%2Bdivision%2Bof%2Bhighways;sort:Pub_List_No_InitialSort%2CPub_Date%2CPub_List_No%2CSeries_No;lc:RUMSEY~8~1&mi=61&trs=160
Now with that said, Old Creek Road is a pretty handy short cut to Morro Bay. Its kind of interesting that this was never a Signed County Route at any point, the road certainly is maintained well enough to be and is old enough to be exempt from current width requirements. Now if Old Creek Road and Santa Rosa Creek Road were combined into one trip that would be one hell of a fun wild hour of driving.