Saw one sorta like this yesterday. The guy said it was a "real 428 69' mach 1", but upon further inspection of his description, it was a "real 429 engine", in a 69' h code. No shortage of tricky word play, unscrupulous sellers, and people who have no idea what they have.
1969 Mach1 - Gulfstream Aqua - 351w 4v
1967 Coupe - Red 289 2v (sold in 1996)
1970 Mach I - Grabber blue, 351c 4v. (Sold in 1999)