I do not take a lot of stock in the FAM because its a 1954 document and not one shred of information is actually from 1950. In this case I am sure its correct, but I am not sure how to proceed.
If I am 1/4" off in the guesswork that is measuring things that are at different heights and planes, the rear fenders will not bolt up properly. Is this something you just wait on until the rest of the sheet metal is ready THEN bolt the running boards up to the rear fender and see where to mark for the mounting holes?
How would you guys do it?
I guess I'm not understanding why you need the locations in the first place. Did you fill the holes where the original brackets were riveted on? Or are you talking about the brackets that were welded to the bottom of the running board?
As far as measuring, I'd lay a straightedge across the body mounting holes, then with a digital level (or even a bubble level), measure back along the frame to the center point and drop a plumb bob or use a carpenters square for both horizontal and vertical positions. It might take more than your two hands, but sounds doable to me. A laser level might help out too as you don't have to hold anything along the laser beam.
As far as the FAM, why would the frame measurements be different over the years.
Hope you can get it figured out.
