Apologies if this is stating the obvious, but on the bottom left of the caliper is an ATE logo.... have you tried their site ???
From the photo's they look to be single piston sliders... something FIAT maybe ??? Also try popping the pads out and see what info is on them - might be able to figure out what the caliper is that way.
As for changing to a different setup, well knowing the spacing between the mounting holes would be the starting point....
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