Odin69, yep, those roads look familiar. Calaveras county, like Placer and El Dorado counties in the 50's before the interstate highways went through.
It's a month or two off but there's Summit Level Road from RR Flat road up to 4 past Avery. And in the spring SPI will unlock the gate at the bottom of Winton Road and you can go up to the top and ride forest roads to 4 near Bear Valley.
A trivia note, that last road with the bridge was a section of Ponderosa Way. That was a 1930's WPA project to build a firebreak road up and down the length of the foothills, before there were a lot of people living up there. Many of the sections have been allowed to be taken over by property owners and are gated.
There was a state inspection of that bridge around 2002 or thereabouts and they found the concrete piers and metal trusses to be in satisfactory condition but the report noted the deteriorating condition of the wooden deck.