There shouldn't be in a '59. The pide frame trailers are from the early years...they stopped around '50. Your frame would be a ladder frame much like our '56 Safari. The only chance you'd have of hitting the frame is to hit a 2" cross member - which would still be bad, but not as likely. It would look something like this:
It's located about 3-4 feet from the front. If your floor is still intact, you can locate it by the ribs where the sides straighten out or use a studfinder. You probably don't have a tank there (we added ours) so you should be good to go somewhere around three feet from the front.