I have the 1954 Southern ABA configuration and I have read the descriptions on the Tandem Associates site. The picture that is shown of an AB configuration has power pickup rollers on the B unit and also power Pickup rollers on both front and rear trucks of the A unit. Also the description given says that the A unit had the horn and battery in the A power unit. Every Southern F-3 (postwar) that I have seen, including my own, has the horn and battery in the non-powered A unit and the B unit has no power pickup at all. Also, both the powered and non-powered A units have power rollers on only the front truck. I know that other Lines F-3 units were built like the configuration shown in the picture but not the Southern or at least I have never come across such variations. Does anyone know if the Tandem Assoc. is correct, because if so, there are more variations than they list?