1.6 will go in and it''s an EASY swap. but you need a lot of parts, (enigne,box, mounts, driveshafts, gear stick assembly, water hoses rad, exhaust )
for a 2.0 it worth doing to a good body shell but IMO as fun as a tuned 1600 can be in standard form they not worth it. 75 bhp and they are relativly thirsty. now if you got a polo 3F enigne and kept the injection it's still a 1.3 so straight swap in , it's better on fuel and it'll go as well as the 1600 and be much more reliable as peirburg or webber most running issues on the 1.6 and 1.8 enignes are carb related