I'm 100% sure that the hood above is not a factory hood, there are many subtle clues but the spot welds are one of the biggest ones, they are nothing like the factory welds. If you post some better pics of the two front corner areas (close ups) I can offer more tips. Also, the two wells in the front corners of the Under Brace are not correctly shaped, the large fixturing/drain holes are missing, and the under brace lacks the Challenger unique features. It's a hood built from one of my competitors hood kit parts, they only sell the Cuda style under brace with thier Challenger shaker kits, they don't make the unique Challenger Brace.
That being said, there were some factory Shaker hoods in that style, they were produced in late 1971 and only a handful actually made it onto a production line car, many more were then sold over the counter, likely as replacement hoods.