Here you go... not easy to get pix of them...
View attachment 374533
View attachment 374534
As you can see, I mounted the feet on the diagonal to clear the toolbox mounting bolts. I also stacked three washers on each bolt between the mount plate and the toolbox to add some clearance for the caster bolts to have full thread engagement into the mount plate.
I'm perfectly happy with the casters, they don't get much use in caster mode, and it's still a beast to roll when needed, but they are plenty sturdy for this application. Looking at all of the ones out there, I got the feeling that just like machines, most of them come from the same factory, and pricing is just marketing. YMMV.