Don’t think I’ve ever seen a 427 Mustang. Plenty of 428’s and 429’s tho.
My son had a 68 fast back with a 427 out of a wrecked T Bolt. It ran high 11’s. This was 25 years ago.
The rumor since the early 1980’s was Carroll Shelby put a few 427’s in some ‘67 GT500’s but 40 years later you think one would have been in a magazine or something or sold at BJ for a few $ million.