Here is a link where you can install Midi to just about any older Organ non-Midi, my friend Frank Pellico, the oficial Black Hawks organist, also he performs at the Aurora's Roller ring, and he customized a Hammond X66 with Midi and also he added other 2 keyboards, so, this monster has 4 keybeds, and all MIDI.
Regards to all.
http://www.artisanorgans.com/
http://members.cox.net/arizonaballroom/Manuel.html