Ok MF, I made a big mistake with that picture. It says in the 1970's not 1970 as I previously thought. So yes if the G4 was started in 73 then that at least makes this picture 73 onwards. It still doesn't explain the black mustang cowling but it could be paint, a prototype or just showing what's coming next? Only the people in the picture will know, I guess.
Thanks for challenging my post! I wouldn't have investigated it more if you didn't put forward a very very important argument! I've said it before and said it again, I'm happy to be wrong as long as I'm learning.
