Mopar has made two different version of their truck and motor home motors on the 318, 360, 361 C.I. HD B motors, 413 and 440. they can come in the regular ratings and the -3 extra heavy duty rated motors, the 440-3 blocks and heads have extra cooling holes in them for the exhaust valves, the regular 440 standard rated home motors don't All the Mopar H.D. dash 3 motors last a lot longer under heavy use
They also have the small 5/8 spark plugs cause there is cooling passages around the plugs to keep them cooler,ran one of these engines in my Jensen Interceptor they where notorious for running hot.
