Attached is a file showing some motorised dandruff, and an exploded still showing the position of the mechanism within the body.
Refinements will need to include: painting the thing, removing the rear half of the side rods, adding MMW side rod detail, maybe changing some couplers (although all my stuff at present has these ones). Oh, and rip off the Westinghouse to have a proper pre-1900 engine.
I suppose I will need to get another top and another mechanism - two was probably the smallest number of engines used at once.
The wheelbase of the Graham Farish Jinty mechanism is a little too short overall, and the wheels too big, but once buried under the wobbly bits they may not be too visible. I found it fitted the top better placed backwards, which has the added benefit of leaving the cab empty.
A key matter for these model engines is the ability of the mechanism to run smoothly, slowly. This engine is close to its slow limit (although it can go slower than the speed seen in the video). For prototypically slow running up a 1:16 grade with a train, we may need to ditch this mechanism and put in MD's proposed horizontal drive wheels (each with separate micro motor) together with a better low speed main motor.
Many thanks to MD for coordinating everything, Peter for the top, and Cabbage for measuring stuff up for the wobbly bits and earning early access to the prototype top.