For me it was about two years before I had to sell and find myself a V8. That being the case, two years is a long time to be a teenager, and in that time I was able to save enough money to afford a V8, and learned to know my way around a classic car (both how to drive it, and how to fix it), and had kept it in good enough shape to sell it for more than the purchase price. Wanting to move up in the world is not a bad thing. It'd be better to get a good condition 6 and enjoy cruising in it and plan for the next car (with a V8) and do that one right than to have to compromize and get a basket case V8 that will still be slow by modern standards.
Your little Z28 example would be a good reason to get a 6 in the first place. I don’t think any of us here are perfect angels. We’ve all had our stop light indescretions, but I think we can all agree that those “illegal contests of speed” are better left to those with more driving experience than a 16 year old. The donor ‘85 GT that I got my driveline from, parted out and sold for scrap last month was introduced to a large tree by a 16 year old. That poor car would probably still be alive (though slower) if it weren’t a V8.