This just in from the Wilwood website:
The D52 calipers made for a 1" thick rotor will work on rotors .81-1.04" thick and 11-12" in diameter.
The D52 calipers made for a 1.25" thick rotor will work on rotors 1.19-1.28" thick and 11-12" in diameter.
Seems you were on the right track all along CaptainFab!
Info from here:
http://www.wilwood.com/CaliperList.a...0Dual%20Piston