The LIRR MOE data sheets show weights of 208,000 and 210,000 pounds for FA1's and FA2's (PC6). That is with the original 244's inside. The dry weight of a 12 cylinder 244 would be in the 30,000 pound range, if I remember correctly. The nominal weight of an FA with traction motors was around 240,000 pounds. If the LIRR data were accurate, the traction motors weighed about 7,000 pounds each (weight new minus weight as PC6). If DutchRailnut's weight and the LIRR MOE sheet weights are correct, converting the FA's from PC6's to PC7's shaved 90,000 pounds: 30,000 for the prime mover and 60,000 for everything else (generator, cooling system, ?).