Depends which flavour you could get your hands on, easiest/cheapest option would be an early carb/ignition lump, but they’ll be rarer now, later ECU type ....starts to get less spanners and brackets and more wiring/what ecu/do you pour money into standalone and throttle bodies.
Are little 16v lumps same bellhousing fit as Cleon/Sierra? If you were to look at an injected lump , may as well throw another handful of valves and another cam in while you’re at it.....just thinking out of norm, everyone wants Gordini , hence that stuff has value, 1.4 16V Mégane in breakers has no value, but depends how much fab you can stomach, and of course whether it’ll bolt to box?