The ALn 663 was a direct development of the ALn 668. Like some of the ALn 668, it uses two 100 kW (136 hp) Fiat 8217 diesel engines, each one powering the inner axle of one bogie. The exterior and interior were upgraded to a more modern appearance, while the passenger capacity was reduced from 68 to 63. Fiat Ferroviaria built 130 in total, some of which came to other private railways. The ALn 776 of the Ferrovia Centrale Umbra was again a development from the ALn 663 that reaches a top speed of 150 instead of 120 km/h. Today, most ALn 663 have been retired due to the introduction of more modern vehicles like the Minuetto. 