Help identifying bumper brackets

[derail]

Hi guys. I usually lurk around the 60-66 forums but I thought maybe you guys could help me out. I recently bought a stepside rear bumper and brackets for my '65 but when I got it home, the brackets definately won't work. I'm pretty sure that they're from a 55-59 but would like to be positive before I sell them locally. They measure about 41" from inside bracket to inside bracket if that helps out. Thanks in advance.