For speed demons — or demons wedded to hellacious fossil-fuel power — the Cadillac CT5-V Blackwing checks off quite a list. A supercharged, 668-horsepower V-8. A top speed above 200 miles an hour. All-day track thrills that would leave any E.V. depleted and gasping, as demonstrated on my endorphin-rushing test laps at Virginia International Raceway.Another feature pushed the Blackwing into too-good-to-be-true territory: a manual transmission. That optional six-speed puts these supersedans (there’s also a smaller Blackwing, the CT4-V) in rare company. Fewer than 1 percent of American cars are sold with a stick.The Blackwings are also among models …
