I bought a 440 out of a late '70s Motor home. It only has 50k miles on it and the guy must have changed the oil in it everytime he had a trip because when I pulled the intake, valve covers and oil pan the inside was very clean. No oil, water or sooty build up anywhere. The RV-3 blocks are very thick and mine had a forged steel crank in it too.
The heads use a smaller plug to give you more room for the wires. GET THAT MOTOR!