John,  Your organ appears to have a similar set of pipes to a roll
played dance organ of my acquaintance, and it will probably have
a similar wind consumption.  This organ has four feeders, dimensions
thus :

  length = 750 mm
  width = 260 mm
  opening throw = 70 mm
  rpm = 56

This speed is as originally set as the organ is still operating from
its original motor, pulleys and chain drive (it has a belt and chain
in series).  Now rebuilt, this organ spends most of its time on full
reservoir travel, i.e., bags of wind.

You will be able to calculate the air  volume rate of supply from the
above data.

Best of luck,
Nicholas Simons