The motor from the Kato 10-103/104 is a good replacement for the original Bachmann 0-4-0 Docksider motor.
Instructions translated to English by Yoshiya Kobayashi – thanks!
At least a limited number – please follow the link below for an update and pictures of all the conversions: BRASS HOn30 CONVERSION KITS by BRICK PRICE
This seems to be an enlarged (!) version of the L.G.Thek Brassworks Z scale ZL01S.E. SW-00 diesel switcher mechanism by Lajos.