You will run into difficulties fitting the 2008 rears to a GC.
The front discs will have the wrong stud pattern unless they came from Liberty STi not a WRX STi.

Also, I know you know better but in case any noobs may read this in the future, do not buy any bolts for your car, especially caliper bolts from Bunnings!

Except for Tino, his car thrives on Bunnings bolts!