Well, I got a problem.
I am trying to set up some blueprints of a Mustang GT (2005) which I got from the blueprint section of this great forum

Obviously I am using Blender, newest version.
I built a "blueprint cage" just like I saw in a tutorial and uv-mapped the blueprint on its faces (side, front, back, top). All manipulation to the blueprint I did was making it smaller so it fitted in the blender window. I fitted the uv-faces exactly to the blueprints.
Now the problem: The views don't fit each other. If I move a vertex e.g. in the front window to the appropriate height on the front blueprint it ends up at a different height in the side window. Thus, I can't model the Mustang.

The same holds true for a blueprint of a corvette C6 I found here.
Am I too stupid? Or is it Blender's fault?
Also: How can I set the plane to see-through so I can see the blueprint behind it?