I would have thought Sherman Pass would be a heck of a work out in an RV and as mentioned, very slow. If you wanted a nice drive through Sequoia National forest then you could go through Kernville (just north of Lake Isabella) and take the Kern river Highway [MR99] through Johnsondale and then M90 up through Camp Nelson to Porterville. Not far along M90 you will come to the 'Trail of 100 Giants', a lovely secluded giant Sequoia grove. Once again it's slow going and a bit of a work out and would take a good chunk of the day up just getting from Lake Isabella to Three rivers near the southern entrance to Sequoia NP, but I drove it in a 30ft RV and loved the drive.

You should also check the status for RV travel on the Generals Highway in Sequoia NP webpage as the maximum recommended vehicle length can become compulsory if there are any road repairs in progress.