1953 Corvette: 150 horsepower
1963 Corvette: 250 horsepower
1970 Corvette: 300 horsepower
1971 Corvette: 270 horsepower
1973 Corvette: 190 horsepower
1975 Corvette: 150 horsepower
The 1970s were dark, crummy times, due to emissions regulations and the oil crisis. By 1981 when the Delorean came out, the Corvette was still stuck at 190 horsepower.
So, building a powerful engine isn't hard, but building a powerful engine that fits within post-1970s emissions standards is.
So it was not unusual at all for something like a caddy to go from 400 gross HP with no exhaust no water pump no cooling system nothing to 250 HP pushed out the wheels.
Now a caddy has a ridiculous exhaust and addons, but even a vette has some. Its highly likely that the 270 HP bare engine and the 190 HP car are the same.
Another complication is HP = torque * RPM I had a commuter car in the 80s with a 2.2L engine that on paper only output 100 HP because its redline was something ridiculous to modern standards like 4000 rpm however the torque (acceleration) was huge compared to my current 100 HP commuter car that winds up like a motorcycle to 8000 RPM or whatever it is. My current car has the acceleration of a 50 HP car but the redline has doubled, so...
Still, cars now are amazing. I mean, you could pick up a $60k 700hp mass produced monster this year. I can't think of the last time i've heard of a tire failing. Stuff is made by machines, they're unbelievably reliable. You should easily get 100k out of any new car.
http://www.nhtsa.gov/PR/FirestoneRecall
edit: I guess my meaning with 'a few' was that it was recent enough to be in the "modern" era of vehicle technology.
Before the change, they would test the engines with no accessory drive, not even a water pump, use headers instead of a full exhaust, and adjust the carburetor/ignition to provide the best numbers per RPM on the dyno instead of reflecting what the engine actually did in the car.
Mr D L successfully persuaded the Allstate Insurance Company to part-fund the two DSV prototypes on account of the safety emphasis.