No dooms dayer here, just an observation. Lack of discernible stampings do not change the history of the car, simply may affect one's perception of originality.
This includes current owner and prospective buyers.
Many cases here on moparts where stamps were lacking and even a well disclosed (barrelcuda) migration of numbers.
Anything but complete documentation always raises eyebrows.
It's almost to some there is no middle ground between numbers well documented and clone. Personally think there is a lot of middle ground..