both can be done.....either head from a g13bb of baleno for sohc and head from gti for dohc conversion
you need the complete head with intake manifold and original gaskit and wiring of the new head....all sensors will be of the head you will be using .....with same head ECU..
alot of these conversion have been done america when swift was offered with carb 1.3 and buying a gti was expensive
still in america and Australia these cars conversion require alot of money but in pakistan parts are not that expensive......
to be better thing will be to replace the whole setup...... though cost saving figure is very low