help identifying bumper brackets

[derail]

Hey guys. I bought a bumper for my '65 stepside with brackets but when I got it home, the brackets are definately not going to work. (I've since done some research and can see now that they are obviously not for a 63-66.) So my question is, does anyone know what they are from? The weird part is they are about 41" from bracket to bracket. Not 34" like normal. I asked around on the 47-59 board but came up empty. Just curious. Thanks