Carl (I really hope I'm remembering the right name), I thought of a glitch with this conversion that may change your descision on whether to go ahead or not. The calipers are too wide to fit behind normal RWD wheels and thus I've used 25 mm spacers and 'front wheel drive' off set wheels.
The Rotors used are WRX STi, unsure of year but BNT part number is RDA650. These are lager than expected on first inspection as I had some Hilux calipers to use but they would not fit over the rotor so went in search of bigger ones. In the end found some Calipers from an 85ish BMW 735i which fitted the bill well. Only needed 10mm (ish) spacers to get the positioning central over the rotor.
Any questions or help just sing out

Tony