No big deal if the 1,000 minimum required for FIA homologation wasn't met because nobody road raced them! Papers were filed in advance "in case" anyone chose to race them. So they aren't FIA legal , who cares?
Royce doesn't acknowledge ( rightly so) the three '67 427 GT500s , one '65 R model , or ten 427SOHC A/FX Mustangs because NONE were "Ford assembly line" built that way. All were built BEFORE sold to the "first legal owner" , but were "engine swaps" after being built on the assembly line with different ( production) engines. IIRC , Ford Engineering "retained" one Mustang for testing the 427 engine package , but it was NOT a W vin . The W code Mustang was NEVER given the green light for production. ONE would not have "slipped out" like the later "one of one" '71 Boss 351 now owned by Bob Perkins. Yes , I know it was repowered by Ford and sold as a 351-2V with changed VIN by Ford before being sold.