What you probably have is a Industrial block. If there was some sort of defect such as core shift, porosity, fissures and perhaps in your case with the std. bore thin cylinders it would not be suitable for passenger car/truck use. Ford would build them for industrial use such as stationary pump, electrical generators. wind generators or any other application that the engine ran at a steady low rpm, usually under 2000-2500 rpm and moderate load. At one time a good source of rare odd-ball engines was the Napa wine country that used industrial wind generators in the vineyards. Some were HD 361- 391s and on rare occasions a 428 engine could be found.
