I try to put my cruising around my peak tq rpm. Lots of calculators out there to help you figure the right tire, trans gear and diff ratio. On my diesel its 1700 rpm. That's about 60-62 mph and I avg 28mpg highway. 4x4, long bed, lumber rack loaded with steel and 2x material plus roll out box. My 65 c10 I watch my vacuum gauge and cruise at the highest vacuum reading. As for big rpm cruising, if your engine revs to say 5000 and you're cruising at 3000. That's only 60% of total rpms, I don't think it will hurt anything. Maybe Lincoln will chime in, the man is a wizard.
