Purlins would be ok but, with all the pipe being free???
The "straw nails" were used for most of the 20th Century for sheet metal covered buildings and many of these buildings still exist today with the need of repair being ever present. Logically then, the "straw nails" are most likely still available. Google search? Anyway they are long "nails" of galvanized wire (varrying length as needed) with a metal "blob"(technical term) stuck on one end and the other end sharpened. The sheet is placed on the purlin, girt, pipe, whatever and the 'nail' is driven through the sheet by a workman on the outside and wrapped around the 'member' by another workman on the inside. Like I said, labor intensive but requiring no tools save a hammer and a pair of "Kleins"(pliers/side cutters).
Sorry, but I haven't lived in Texas for over 40 years and I doubt it is anything as it was when I was a kid. Besides our ranch was actually in Newman, NM now part of the White Sands/McGregor Missle Test Range.
Rod