To get the 5300 rpms out of the generator, 

½” pulley on the dynamo.  

For our engine, the flywheel is 2.5".  5300/5 = 1060 rpms roughly.

These steam engines typically run at 500 RPMs and the boiler works hard for it. 

So finding an engine with 6.5" dia. flywheel would be ideal. 5300/13 = 410 rpm roughly

Choosing the right pulley size and flywheel diameter is crucial for optimizing the RPM of the generator. Your calculations make sense, aiming for the ideal RPM for efficient operation. Good job on the analysis!