I had a '74 X-1/9 and after I replaced nearly everything in the engine except the block (I did have that bored a bit as I recall) with aftermarket parts and changed the gear ratios it was great. Once that minor stuff was taken care of I also had 125 hp rather than the stock 72 and still got super gas mileage, almost thirty on the highway in fifth. And, it was reliable, too.
So you see, having a good Fiat is just a matter of taking care of a few little mechanical details.
Well, some minor interior stuff as well like the window raising and lowering mechanisms, the door locks, the seats, and the heater. Just little stuff, you know?
;-)