Good to downshift 68rfe

Is it good practice to downshift and keep my RPMs between 2,000 and 2,500 when climbing a long 6% grade? I’m running 35s and usually drive unloaded. My 68RFE has 150k on it and was surging, so I scheduled a rebuild. However, after I replaced the fluid, filters, and added a deep pan, the surging completely stopped. I’ve since driven a few hundred miles, drained it, and refilled it again.