sadly im with the lads on this one.
alot easier to sell your own,and buy a factory built punto hgt 1.8.
the hassle of getting a 1.8 engine,ecu,coded key from donor car that engine came from,gearbox change,another rad needed ,wiring loom etc.
and then you have to beef up the brakes,front and rear,stiffer springs to cope with new engine.
you would have to buy a hgt to do the conversion
best buy a hgt 1.8,or buy a modified punto to a higher spec like a 20v.
but make sure its been done to a good standard and passes mot's/sva test.
alot of 'freds with sheds' death traps built in back gardens.
best of luck with your project what ever it ends up being