Hello Thomas,
(Except in the case of unified/extension organs, such as theatre organs, or similar 'borrowed' stops) the rank's basic pitch makes no difference to MIDI note number range -- middle C on an 8' rank would be note number 60, as would middle C on a 1' rank. The pitch of the rank is instead specified by the Rank.Pitch_RankBaseOutputPitch64ftHarmonicNum attribute.