Checked online and you are correct on the ratio depending on the master cylinder bore size, see link.
http://www.mpbrakes.com/uploads/docu...alratiopdf.pdf
Re calculating my assembly (I measured the clutch pedal not the brake pedal). The brake pedal is 12" from pivot to center of pedal and the brake rod hole measured 3.75. Which equals a 3.2-1 ratio.
My pedal assy is probably still the same as yours, just trying to get the correct calculations.