Can I put an older engine in my Focus?
That that older engine will certainly physically fit, but you still could have huge issues with the electronics and the engine control unit (ECU) talking to the ignition keys etc. We wouldn't recommend doing this unless it's done by someone that has done the same kind of swap in the past. Even then, it's undoubtedly a huge a mount of work.
Shane O' Donoghue - 01-Aug-2019