Redstone, the FADEC version of the GE engines became available after the first five B763's were delivered but Qantas management with all their wisdom decided that, for future aircraft acquisitions, it would be better to stay with the standard engine and have a common fleet rather that operate a mixed FADEC/non FADEC fleet (which is what Air NZ ended up doing with no problems). This decision appeared to be vindicated when the Lauda Air tragedy occurred with reverser deploying during climb out of BKK. The engine in that case was FADEC and a number of people initially were saying that it would never happen on a non FADEC engine. Subsequent modifications were applied to all engines (GE/RR/PW) irrespective of the engine management system.
The only reason that OGV was ordered with FADEC engines was that after OGU was delivered, Qantas purchased three second hand GE (FADEC) powered B744's (otherwise known as the "ugly sisters"). Therefore, having FADEC engines in the engineering system already, it made sense to order OGV fitted with them.
OGV also has a different Leading Edge Slat system to the rest of the fleet as it came off the production line just before the first of the B767-400's. Boeing had designed a lighter, simpler & more reliable LE Slat system for the B764 and OGV benefitted from it.
Bankstown & Lancer, you are correct - it is only the last three aircraft fitted with GPS/Pegasus. My bad.