Fiat Seicento engine swap

[Dark99]

So i found cheap and good fiat seicento 1.1 40 kW, AC, 2002 year of production, in quite a good nick for the money, but it has problems with overheating, cooling liquid boils after shorter time, and I don't know the damage already made on engine, so i would like to buy it and do the engine swap. I don't need any kind of performance engine, just something reliable, cheap and easy to fit into the car without modifying too much if possible, and easy to work on and maintain. So i would like opinion on what kind of engine from which car should i look for? Thanks in advance.