The Heavenly Kid (1985)?

If any of you have seen this could you help me with something?

This is a really good movie ;however, it appears to have a major plot hole. The movie is about a teenage boy who dies in a car crash sometime in the late 50’s. I am guessing that because all the girls in the scene where he dies are wearing poodle skirts. The guy himself also looks like he is dressed like someone from the late 50s or early 60s. The whole scene looks like this time period as far as I can tell.

Anyway, he comes back to be a guardian angel to his teenage son in 1985. I’m just guessing here but how does this guy have a son who is still a teenager in 1985 when he died sometime in the late 50s? If the son was 17 years old, that would mean he was born sometime around 1968. How could this be?

If anyone has seen this movie could you please explain this to me? Maybe I’m wrong about the cars and the fashion trends of the late 60s but it appears to be much earlier. I apologize if this is a stupid question . My knowledge is minimal.

Anyway, thanks

 

The movie begins with the caption "The Ridge... Early 60's."