I Almost Died Today!!
I remember scary stuff as well.
I was a bit older than 15 (early 20's), but I had a '69 Dart that I was building as a drag car. I had the car up on jackstands...all four corners in their proper place. Mind you, the car was very light. No motor, fiberglass doors and bumpers. No interior (window cranks removed, lexan widows, ect.).
So i was putting the 8 3/4 rear in it. It was being a bit of a *****. I pushed up on the rear as hard as i could and I lifted the car off one of the jackstands while under it.
I set it down very slowly and got out underneath it as fast as possible. I rearranged the jackstands, but it took me a day to get the courage to get back underneath it to complete the rear end.
Things like that you never forget.