Looks great man.
The only thing that is detracting from the realism in the eye is the window reflection contrasting from the background. The original background could have been high noon at a glance, the shadows weren't all that prevalent. In your addition to the background, the hue makes it seem like the sun is setting, hence the shadows are more prevalent to the eye - then you get to the windows which are not the same hue as the reflected background, instead they're the same as the original car shot which was clearly not taken at sunset. It's such a minuscule thing, but I think it would add so much to the shot if the windows had one of those little glaring blinding spots and a reflection of the sun going down over the cliff. As it stands now, you have a nice sunset with windows reflecing overcast.
Damn, did I explain that enough?
Besides that and those fugly wheels, I love every idea you had with the car from the hood bulge to the side mirrors.
