1,9td has 2mm larger piston pin and ~4mm taller piston than 1,6.
I doubt 'caveman' will really want to crack the oil pan to take some pics and have a look see but either the 1.7 comparatively speaking has specially made 1.9 TD pistons that accommodate the differences to match up with the 1.6TD rods or specially made rods to accommodate the differences in matching up with 1.9TD pistons. Then rods may be totally different too - like slightly different in length, but I am thinking crank would most likely would be the same as 1.6.
Stephen
Thanks Andrew!!
I appreciate the pics and info!
I see that you are not Joe the plumber but rather Andrew the pumper!
I'll keep that in mind when I need a rebuild for one!
Thanks again!
Stephen