Richard, I have owned (4) different 715's and believe that I have every piece of 715 IH sales lit ever offered.Here are the specs taken from them.
C301 gas rated at 107 hp at 2400 rpm
D301 diesel rated at 95 hp at 2600 rpm
D310 German diesel rated at 95 hp at 2400 rpm
Out in the shed I have a 1978 715 D310 powered with RWA and also have a 1975 gas 715 hydro parts combine with good C301 that will be going in to a 1961 Farmall 460 gas tractor.
Combines are rated at flywheel horsepower where a tractor is rated at pto and drawbar hp.