I recently acquired a 292 and I assumed the oil pan plug had been previously damaged. To drain the oil, I had to remove a square headed 1/4" (or less) bolt inserted inside a larger bolt. I believed this was a repair from the original bolt being stripped out. After removing the oil pan, it appeared (from inside inspection of oil pan), this was not a repair. I checked the oil pan on my 256 and its identical (square head bolt threaded into larger bolt). From inside the oil pan, this creates a condition that will not let the oil drain without holding the oil sediment and sludge in the pan. Looking at the inside of the pan, there is a 3/16" rectangular plate which appears to have been initially welded to the bottom of the pan on the assembly line. This is on both oil pans. Was this original by design from the assembly line?

Darrell Howard Whitefish, MT Outlaw 56 Ford F-100's