You might can simply get a shop to take what's called dedicated measurements. All cars have holes at various places in the frame or unibody where cross measurements are taken from, to check what's called a "diamond" situation. That's where the car's frame rails are essentially a paralellogram (diamond) instead of a rectangle. The holes are recognizable because they have a "lip" that protrudes into the hole all the way around the hole's perimiter. There are special tools designed to fit into those holes for the measurement to be taken from. If you can find what the spec is supposed to be for your car, you might can even do it yourself.