Almost sounds like "Corvette Summer" except for a few details. In that movie, a kid builds a really nice Corvette one-of in high school auto shop (not nuclear powered) and it gets stolen on it's maiden voyage. The kid becomes depressed and leads a crappy life until he learns that the car is in Vegas. He goes there with almost no money and makes friends with a prostitute-in-training. He then lives a crappy life in Vegas just trying to survive. He does find his car in the end and gets the girl. This movie was made in 1978.