Model B frame questions

[deuce_roadster]

All x members should be riveted in, none came bolted. If the x members are a set and the "K" indeed is early without the legs, the front should be flat where the motor mounts go, no depression for the biscuit. Rails could be anything, if you can read a VIN number that will give you some idea on the rails as to when manufactured. It was obviously pieced together from maybe as many as 5 frames. Also, early "B" VINs started "AB" then the number.