rpm sweet spot on class A with 365hp v10 for mpg?

Since there aren't a lot of variables with the V-10 besides wheel size, the other posters have given you the info you need....somewhere between 60-65. I find that all RV's have a spot where they settle in and run their best. For example, that may be 62, 63 or 64. Drive it for awhile and see where it likes to run.