It looks to me like you have the standard Roadmaster base plates (we have them on our Jeep). Is there a cross hole in there square tubing for a hitch pin a few inches from the front of the bracket? If so, I would say they are Roadmaster.
If so there are two adapters for your Blue Ox available. The first has a fixed cross bar, which means you have to remove the hitch pins and remove the entire bracket as an assembly. It is the cheaper solution and can be viewed here: ROADMASTER BRACKET TO BLUE OX OR DEMCO TOW BAR ADAPTER PART 033
The second can be removed a piece at a time and is a little more expensive and can be found here: ROADMASTER BRACKET TO BLUE OX OR DEMCO TOW BAR ADAPTER PART 032
I would suggest you call Roadmaster to be sure.