This is from the movie Highway with Jared Leto and Jake Gyllenhaal:

http://www.imdb.com/title/tt0165361/

I was going to make a page for it but I accidentally returned it. There aren't that many notable vehicles in the film, only this hardtop turned into a convertible. The two main characters go on a road trip with a girl that they meet. The girl (Selma Blair) tells them they are doing it the wrong way by not having a convertible. So Jared Leto takes a rotating saw and cuts the top of the frame off while Jake Gyllenhaal is still sitting in the driver's seat asleep! John C. McGinley (Scrubs) also plays a hilarious role. I would recommend this movie if anyone wants to make a page for it, I'll probably make one someday...

Does anybody know what kind of car this is?? Any guesses at least?

Earlier then '68, since it has no side markers.
...
That's all I got.

There are of course many more shots of the vehicle, I just chose this because he cuts off the roof with the saw. Since it used to be a hardtop it's especially difficult to figure out.

Blarf, I was way off, it's a '70-'72 Monte Carlo. The side markers are hidden in the trim.
If you remember the front end; an eggcrate grill means it's a '72, I can't find any external differentiation between '70 and '71.

Nice! I think you nailed it. I really had no idea what it was. Thanks!

Thanks for the tip, it's added now: http://www.imcdb.org/movie_165361-Highway.html