Mk2 RS Mexico was a pinto
the GT or mexico 1.6 is a much better engine than the standard 1.6 but seeing as they both go in i'd allways start with a 2.0 unless you have a tuined 1.6
You'll need RS2000 mounts and sump/oil pickup at a minimum, RS BH would be nice as would the alt mount but not essensial you'll need to cut the rad support to get the rad further forward as well cos the pinto is longer than the Xflow