I have been quietly following along with this build since the beginning, and I just wanted to chime in to add my kudos for this
fine project. The proportions, detailing and functional running of this model are terrific. Very nice work!
If you do get a dual-shaft motor in there and drive both trucks, the side rods would be MUCH easier to make work. You won't have
to worry about a free-rolling truck turning those cranks in quarter. Just tack them onto the axles, let them go around for show,
and they can have some slop in the holes and not even be exactly quartered (and they will still work).