A couple of years ago my Father asked me to build an organ with an arranger in (based on a Hammond M44 as he couldn't sell them on their own) originally he wanted to use a Tyros, but the drums and accompaniment didn't suit the sound of the Hammond so well and used a Ketron module instead.
http://www.hammond-organ.com/Products/hz_projects.htm I didn't make it from the ground up though and used the original lower half of the cabinet and lid. With the help of my brother-in-law we made new side panels and a steel enclosure to mount the PCB's and other items for the module. the whole thing was done in kit form hoping to sell it to M44 owners in other countries but Hammond withdrew the M44 a short time after we finished it.
TWD