alright mate, the mk1 is a 1.3 and the mk2 is a 1.4 and is almost the same engine as ur punto gt. the turbos are both T2 in mk1 and mk2 but the mk1 turbos are made by IHI and the mk2 turbos are garrett. the mk1 block is meant to be a little bit stronger but as for modifying them, both engines are fairly simlar to modify. the mk2 1.4 engine tho has a much much better gear box with a taller 5th gear and is capable of highter top speeds. over all i'd get a mk2 as the interiors of these are nicer and the look of the car is nicer (in my opinion) and the engine is slightly more modern and u'll know the engine better having owned (or own) a punto gt.
hope this helps
Dunc
Dunc