An interesting diversion from freeway driving is to take 99 south from Stockton, then take CA 43 at Selma, south of Fresno. After a couple miles of city traffic, 43 is a nice rural road that parallels the railroad tracks all the way to Bakersfield. It also bypasses most of the rough road sections of 99.
If it's open, an interesting stop is Col. Allensworth State Park, a farming community founded by free Blacks after the Civil War and later failed due to water problems. It has a visitor center, several restored town buildings and homes, and a campground for smaller RVs.
Take Lerdo Highway east from Shafter to return to 99. It's a rural 4 lane divided highway and you'll avoid the truck traffic on CA 46.