Ford already has provided an early look at its freshened 2018 Mustang lineup, which goes on sale this fall without a V-6 model between the base turbocharged four-cylinder version—now with more power—and the Mustang GT with its enhanced 5.0-liter Coyote V-8. But the V-6 wasn’t the only pony missing from the stable; the most awesome Mustang in history and a reigning 10Best Cars winner, the Shelby GT350, also was M.I.A. And if the headline of a recent press release from Ford is anything to go by—“Ford Extends Shelby GT350 and GT350R Mustang Availability to 2018 Model Year”—the automaker...