Hard to beat the R280. We used the DC6 for firebombing and were brutally hard on the engine. One day on short turn fire we did 11 wet max gross takeoffs in 1.1 airtime. Right after takeoff we were at the fire, back to 25 MP and then back to METO to climb away from the drop
But unlike modern t/prop and jet engines... the engine life of a big radial is directly proportional to the skill of the flight crew.
Bottom line: There is no better sound in aviation than a 4 big radial engines at cruise RPM leaned out and sync'd up.