The cars have been around for forty-some years.  Same goes for the sum total of replacement parts, components, pieces and chunks.  They are old, cranky and warped by any number of variables:  time, re-manufacturing methods, storage conditions, handling and too many other unknowns. 

It is up to the restorer to respect and work within the limits imposed by history and technologies of a generation or two ago. 

Restoration work is about reaching owner's objectives while preserving historical integrity of the vehicle.