K member 73 Duster 318
http://www.forabodiesonly.com/mopar/showthread.php?t=307984&highlight=frame+rails
check out this members rails for sale-- use them as a guide as to what yours should look like, they look to be prime pieces of metal.
i do not have any affiliation with this seller-- i just think he does an outstanding job on removing pieces from cars.
1 bolt?? that is scary-- you really need to start checking the car out-- sounds like it was put together rather quickly.
Lawrence