Picked this up for the atom drum wheels, and wound up being really intrigued by the frame. Trying to figure out what it is/ what it might be worth so I can decide whether to build or sell. It had a schwinn train/ plane head badge but not sure if its correct for the frame since a few other bikes bought with it are all made up of mixed parts. It has a serial number stamped under the bottom bracket, SD 916 58 and LB stamped three times. Any help is appreciated