Firstly, this will get a better response if posted in the section for the car.
Early Bravo/Brave models I don't know about.
Later Bravo model will be computer controlled.
If the engine is computer controlled, replacing with anything different will be difficult. Using the original engine ECU on any different spec engine may not work properly, especially if moving from 1.4 to 1.6. If you get the engine from a donor vehicle, you'd need the engine ECU, and Body ECU together, and the ignition key, as both ECUs need to talk to each other, and both accept the microchip in the key. If the donor is a lesser spec than yours, it will not recognise some of the additional stuff, e.g. electric windows, aircon, foglamps, etc. A higher spec ECU can be told to ignore stuff it does to have, but a lesser one does not have the info in it to activate.
Replacing like for like is the easiest option. Good luck.