Hy spanners, after checking one of my Motor's manuals I think your truck might be a 1951 400-27, they were built from 1951-54. Possibly tractors did not have a fuel tank filler necks and fuel tanks in the cabs, I'm not sure. Smaller trucks did not use the 270 in those years. This is operating on the assumption that the engine has not been swapped, hope that helps.