i understand "free", but i'm still not sure how you'd use this motor in
this case though.  the hx motor is very finely tuned [with fuel economy
in excess of the civic hybrid] and trying to replicate this efficiency
is non-trivial.

the engine computer for this motor expects to see things like road speed
and oxygen sensor readings.  you can wire this motor to give those
readings to the ecu, but you need to know what you're about, and the
expense of custom parts to achieve this will probably exceed the cost of
a used diesel motor whose engine management is trivial and whose fuel
efficiency is a given.  using non-honda engine management on your hx
motor probably won't give you good efficiency results.

what i'd do is look for a used pump engine [from a building sprinkler
system?] or something like that.  cheap/free.  easy to manage.  no gearing.