The dual piston S10 calipers use a different steering knuckle than the standard single piston, the mounting systems are completley different. They aslo use a different wheel bearing arrangement, with the dual piston type using sealed hub assemblies (like a FWD car or late model 4x4) and the single piston using the old style spindle/tapered roller bearings. The rotor is also different.
Now to my opinion, I would either get the rear axle redrilled to the Chevy pattern, or the rotors redrilled to the Ford pattern, either way would be fine. While turning down the rotors as Jerry says would definetly work, I would be concerned about the reduction of the brake surface area as well as the cooling fins inside the rotor, it could cause some strength and cooling issues, as well as reduced braking power.
One other option, dual pattern wheels. Many aftermarket wheels are made with 2 and sometimes 3 bolt patterns. That could be a viable option.
