MFG RPM/hp specs?
In the last couple years there have been several articles in Model Airplane News by a couple different authors about this very subject.
There's a formula:
HP=Torque times RPM divided by 5252.
This formula is run through all the torque values at the different rpms to figure the horsepower curve.
A pretty good measure for the laymen type is to use some fish scales behind the model with different props to see how much pull it has. This would be static thrust. But this has it's limitations because you have to stay within the needs of your airplane's design for a certain minimum speed (Pitch times rpm)
Jim