Not sure in the GQ platform, but seem to remember the RB were all pretty mix-n-match from the holden camaro(?) commodore(?) to the datsun 350 to the later nissan skylines...
All same bellhousing patterns. And they would fit a toymotor celica box behind em...

Unless the 3.0 is dead, why not bore it to 3.2, fit a stroker crank, hot cams and double or treble-carb it.
WAY cooler that a 25T.