The Ford GPA “Seep” (Government ‘P’ Amphibious, where ‘P’ stood for its 80-inch wheelbase), with supply catalog number G504, was an amphibious version of the World War II Ford GPW jeep. Design features of the much larger and successful DUKW amphibious 21⁄2-ton truck were used on the GPA, but unlike these and the jeep, the ‘seep’ ...