The serial number section of the Vanpelt site referenced in post #4 can be reached at: http://www.vanpeltsales.com/FH_web/flathead_serialnumbers.htm You will know when you have found all of the numbers since the whole number started and ended with a 5 pointed star. If the vehicle originally had a V8 engine after the beginning star there will be an "18" followed by the serial number from Vanpelts. Van pelts site does not include the 4 cylinder vehicles. They also had a star before and after the whole number. In the case of the 4 cylinder the first digit was "B" followed by a serial number between 5263535 and 5292536. They did not make that many more 4 cylinders, the serial numbers skipped the first 5 million numbers since they had been used for the Model A.
They can be about anywhere, the information provided is the most common locations. They are often not easy to see, I have had trouble finding them on bare frames. They are there, just takes a little detective work to locate them.
Ford's instructions to its various assembly plants to stamp the number three times on the left side of passenger car frames, but only once on commercial frames as in some cases the rear two numbers would be exposed in plain view tempting those inclined to foul play.