When the GTOs and Lemans cars were only a couple years from being new there were tons of Lemans/Tempests with GTO parts on them. It's nothing new to put a scooped hood on either car, along with some of the other identity parts.
At the other end of the spectrum, back in the day, you got a lowly Tempest and put the GTO running gear, or a big car 421/428/455 engine in it with 326 emblems on it, and surprise that SS chevelle by beating him at the stoplight to stoplight exhibition of acceleration...........
Anyone that knows about these cars can usually pick out a real GTO, over a clone, but if you think about it how many Lemans/Tempest bodies gave up their lives to resurrect GTOs already. The GTO is the top of the line for A body Pontiacs, commands more money, and is usually the most desirable. It's always going to be that way.
Problems crop up when someone sells a clone as the real thing for real car money, then someone's feelings, and their wallet gets hurt. It's fraud, and that is in the eyes of the law.
Some people would rather own a clone, and be able to drive it as if it's a real as born with rare car, they're just too valuable to drive on a regular basis.