how do you distinguish between accurate and non-accurate car diagrams?

hi everyone.
Im a beginner in blender and am trying to learn how to design cars using background images of car diagrams from the internet. I recently found how to set up reference images correctly in blender i.e aligning top, side, and front of the vehicle and using the cube to create a correct proportion etc. however when i start drawing away a portion and for example the hood of the vehicle i find there is a dicrepancy between two ajoining view points of the image.This consumes time since once id stated drawing i suddenly run into proplems and have to scrap the design and start again. on some tutorial videos the artists state that diagrams can be accurate and some not accurate. how do you distinguish between the two. Does anyone know any website that provides good car diagrams. thanks for your help and advice in advance.

CAD print from the 3D design model will give you accurate prints. Scanner that is designed to scan engineering drawing can produce accurate image file. Other then that the accuracy is in question.

If you need accuracy, collect as much information as possible until you get a good understanding of the design. Hard dimensions are always good to have.

Also, remember that real product that is made from a design drawing have some allowance built in. The hard dimension on the drawing may not equal the real thing.