So that you know, that picture doesn't show it but the two bolts on the right are directly behind the brace you can see. You have a couple options. Use a spanner/wrench (either standard or ratcheting) or a 1/4" ratchet with an extension. The holes you see in the brace just happen (maybe by design?) to let a 1/4" extension pass through, then you can use a regular ratchet on them, you just have to put the socket onto the bolts first, then pass the extension through and into the socket.
On a side note, it's amazing seeing how rusty everything on that bumper is compared to mine. Being in a dry climate really makes a difference, and we salt the roads here too so it's not just that.