Ford showed an early prototype of a four-door Mustang at a dealer event last week, according to the Wall Street Journal and Automotive News.Dealers said the sedan is roughly the same shape and size as a Porsche Panamera, and executives claimed it would hit 60 mph in under four seconds.The Mustang sedan is reportedly slated to have a starting price of less than $40,000 and enter the market in either 2028 or 2029.