Engine harness is possibly wrong, but its easy to get a RHD 4x4 one (I'll sell you one
) The car loom will be different too, for things like central locking etc, unless the 1600 has that already?
Also the ABS pumps are different i think? they are drivers side on both LHD and RHD cars, so at the very least the brake lines will need redone.
As for the transmission tunnel, i think late 2WD cars had the 4x4 tunnel? Its easy to see the additional 4x4 bulge from the passenger compartment, so you could literally just go and look at both shells?