This will work.  It is legal to put a newer engine into an older vehicle and
you can get a nice power boost.  You can use the 1.9l exhaust system, and
injection setup on the 2.1l from the syncro.  I have never done this before
but Dennis Haynes did it for a customer of mine a few months ago.  The
customer was very pleased with the results.
Have fun.
Ken Wilford
Van-Again
John 3:16