Pics look good. I might suggest trying a different angle (I'm sure you did, but you only posted one angle really).

Avoid distracting background elements, or emphasize them. For example, the stairs sign. Either use it to your advantage or leave it out... you've done neither here.

The side of the Mustang that you're showing is in the shadows... it's dark.

The truck is the strongest of the pics IMO, but it has a few flaws. Try to clone out the sign and the fire strobe in post, if possible. Also, the door frame should be parallel with the edge of the frame. It looks like the door isn't vertical. There's no detail in the grill area, just a few highlights. It needs more light from the front so that you can see the details.

The Firebird is second. It too has the prevalent side in the shadow, but not as much. The sign and strobe look weird again. Door looks good this time. There's an odd blue light showing from under the hood, clone it out IMO. Finally: you've lost detail in the tires (mainly the rear one). I can't see if there's a tire or a floating rim there... I know the laws of physics, but it looks weird.

Hopefully you won't take these things as insults, but constructive criticism. I enjoy helping people better their photography and I really feel that this is the best way to do it, but all too often people get upset when they get real constructive criticism.

Overall you've got a great start. If you've got the funds for an SLR, go for it... you won't be disappointed.