I have found with some manufacturers schematic drawings of every measurement imaginable, presumably done in the design of the car. You can then compare every measure with a car you know you can use. I did this with the present peugeot 3008 and the old model 3008. I found a difference of only 6mm in a crucial measurement, thus enabling me to say with certainty that I could use the car. You could even with the right photoshopping skills overlay one over the other.