I saw that in your second picture, those calipers have a lot of meat above the pads, which is strength of course. I began with 65-82 Corvette calipers, and those have 1.875" pistons. They were a little big, but the pads were cheap and I swapped to SSBC calipers. Those I didn't know used non Corvette pads, from a Mitsubishi 2000 GT(smaller pads). Those don't last long enough, so I'll try the Wilwoods next, with 5.5sqin of pistons. Those will also be a little big, so a Ranger MC is my best choice to reduce front brake power a little. If the caliper pistons weren't so big, I'd go to the 01+ spindle and use a 13.75" rotor. That's too big though for these calipers, who knows what master cylinder that might require.
That's why the 12" Sport Trac etc, front brakes are the only decent feasible upgrade. Something like the Aviator brakes would be next, with the custom bracket and 17" wheels.