All depends on the weight, terrain, coolant temperature and even wind drag of your car or truck.
My unloaded 4200 lbs. 1/2 ton truck and late 235 with 3.55 rear can go 2500-3000 rpm all day on relatively flat roads.
My 3000 lbs. coupe with a late 261 could go even higher with little drag or load on the engine...
On longer trips just keep an eye on coolant temp and oil pressure.
