Never go by advertised RPM ranges, ever. Mine is 3500-8500, makes peak power at 5,900...
If you don't understand basic camshaft tech, call and have a custom grind made for your specific needs / wants.
Looking at a 273 engine, i'd be picking my cam in an attempt to overcome it's limitations. The 273 has a cubic inch displacement that is as small or smaller than a 6 cylinder, is head limited and intake valve limited. It's iron headed, so it's more fuel sensitive as well.
So, hang the valves open longer, lift the valve only as far as needed and widen your LSA. The wider LSA will help with the octane requirement and also improve the idle you are saying you want.