Guys I am having a difficult time measuring my 70 Dodge Challenger for squareness. I have a factory service manual and have referred to the info there, but I feel their diagonal measuring points are very vague. So it is hard to tell where the actual point are to measure between. It almost seems as though they are "in space" somewhere. I guess I am looking for a hard fixed point to measure between.

If you ever look at some GM schematics the measuring points are very clear and deliberate. So I am hoping someone more knowledgable than me can clarify or show me where the points actually are. I would like to check for squareness. This information would also be helpful if someone was wanting to build like a frame table for body work. Maybe we can work as a group to come up with a more detailed frame dimension sheet for all to freely use.