Hello, I bought a set of shackles this week that are supposed to fit the M37 but they're slightly too narrow. Does anyone have any idea what they're for? They look like the M37 bumper shackles and have the off set pin so that they'll hang flat against the bumper. And they use a 3/4" pins like the M37 shackles but they're slightly too narrow to fit the M37 brackets. These are about 15/16" inside at the pin holes. Overall length is 4 1/2" and they loop is 3" across on the outside.