You need differant caliper carriers and a set of 312mm disc's.
I found it easier (although more expensive) to buy new calipers too. This way i could paint them off the car and then change them all over at once, rather than mess around cleaning up and painting the existing calipers on the car. There normally grotty and you can't get as good a finish. Had to do this with my rear's and it was a PITA.
I sprayed my front's with plastikote red.
HTH Sam