Find top dead centre at crank and with the distributor @ #1, mark the rear of the camshaft pulleys and the head, as long as all the reference marks are in sync when the belt goes back on all will be good. You have the Holden to drive so it doesn't matter if you take your time to do the job. Be carefull when you remove the belt not to move the dist drive pully as this will put the igniton timing out. post #4 in this thread shows how I marked the camshafts
Well, while testing the alternator on my son's GTV 6, I noticed some antifreeze drops and tracing them down, I found the water pump pulley has a slight wobble and the seal's weeping. So now we got a water pump/timing belt/tensioner job in our near future. I had heard a bit of a whine lately...