Help me to understand Jacob's Ladder. (UNBOXED SPOILERS)

I’ve seen that short movie, and I liked it. If memory serves, I think I saw it in my psychology 101 class.

I have not seen JL in years but I remember leaving the theater thinking about what I thougt was a fairly serious plot problem.

If in fact the whole movie is just a vision or dream out of Jake’s subconcious during the last few seconds or minutes of his life in 1960’s Vietnam, how could he accurately envision exactly what 1974 or 1975 would be like in his dreams?

For example, during one scene (IIRC, it was a long time since I saw it), Labelle’s “Lady Marmalade” is playing in the background. Lady M was not released until 74 or 75. During another scene there are characters driving what I believe was a 1975 Ford LTD. There were a few other examples, but I can not remember them right now.

If these are just battlefield visions, how could his subconcious create these things accurately? Wouldn’t he just envision things that he has already seen during the time period? This little plot problem confused me and made me think that maybe all these things happened years after the battlefield injury.

That is why I was a little angry after the movie, that and it seemed that they tacked on that little bit about drug experiments on the end- kinda like saying “All this time you thought you were watching a movie about soldier drug experiments- but you weren’t, we pulled a “Dallas” on you, but hey there were drug experiments on soldiers during the war- maybe you will get to see a movie about that some other time”