Upper control arm mounts/shock tower

These are from classic industries also
I would map out the whole car much like 72bluNble suggested. That will give you the whole and real picture of what you are dealing with. You can't assume anything on these old cars or new cars for that matter.
One thing this map will not tell you is height. Datum is the word. Uneven heights can change lengths an width measurements. They all have to be taken into consideration. L,W, and height.