Mohsin Sb.
Was the GTO in question orange? It's a shame what he did, especially since it's a rare car as is. And the fact that engine parts aren't too hard to come by, he could have repaired the original powerplant.
I've seen a bunch of people getting injured when using badly modified cars. Usually, the brakes and suspension aren't up to the task of coping with the increased power. Then there's a question of weight distribution and chassis integrity, all of these are put into question with wild engine transplants.
That said, there's no harm in modifying a car responsibly (not only for your own health, but also for others'). Although people who go this route are very rare. As far as horsepower is concerned, it's hard to say "enough". finding the proper balance is an art form in its own right.