I've been down that road to the end but didn't see any OBVIOUS road heading east up and over the ridge.
I have an old map that shows County Road 78 or 78A going from the Capay side west up to the radio/tele towers up on the ridge. I would have to be there to service the equipment but usually those roads have locked gates.
I'll have to give it a better look next time.
Talking with the owners of VeloCity in Winters some time ago. They said that there was some movement afoot to complete this loop (with a multi-use trail whatever that means) from east side road. The only two possiblilties would be to have it go over the top to Capay OR (and this would be very cool) to have it link back up with Hwy 128 by coming over Monticello Dam.