No, because the two engines will likely have significantly different volumetric efficiencies. This difference will cause the less efficient engine to use more fuel to make the same amount of power.
Would the volumetric efficiency be related to the max rated hp, or is it independent of max rated hp?
This is all really interesting to me as I've been struggling with similar questions at work related to HP, load factors, and brake specific fuel consumption in ag tractors. Since you obviously know what you're talking about, do you mind if I PM you?