Engine ecu and immobilizer would need swapping from donor with keys if all are lost, not sure if the reader around the barrel also needs to be done but think so as swapping the barrel should also be done.
If you got the code card and can get ignition on, you can tap the throttle pedal as in the manual with the numbers from the code card to disarm it and start it. Code card should get you new programming key if Fiat still does them?
Also if someone still has old programmers and knowledge you could get the current ECU reprogrammed to remove the immobilizer and get locksmith to decode the keyblanks.