Here are the mounts from Amazon
The racks just sit down in the factory "stake" pockets on the machine. They go really deep on the Kubota so by sliding them in and adding the cross brace they won't move. I can load the bed with firewood and dump it and they don't slip or come loose. (We have the Elec. dump so it is really handy).
As for the bolt heads- thanks for the suggestion. I was planning on cutting them off and adding acorn nuts but honestly sort of forgot about it. I do need to get them taken care of!