When I worked on this car in my TL, I developed a V8 for the car, developed by John Judd for the purpose. The engine is V8 based on two sets of Vega cylinder banks attached to a common crankshaft, using steel cylinder liners, aluminum-alloy crank with seven main bearings and aluminum heads to avoid the engine wear problems the Vega had. The engine's head a double overhead cam, four valve per cylinder designs with internal agitators before the combustion chamber to improve the air/fuel mixing. The engine used Bosch electronic fuel injection, a high-pressure cooling system and dry-sump high-capacity oiling to improve the cooling of the car and improve its reliability. The end result with a conservative tune was 320 horsepower and 310 ft-lbs of torque from a 4.6-liter engine, pretty wicked numbers for 1981. The DMC-12 of my world turns the engine around and mounts with the back two cylinders over the rear axle (which is why it uses dry-sump oiling, to lower the center of gravity) and puts the gearbox in the middle of the chassis backbone (which helps stiffen it, among other benefits), resulting in the driveshaft going back the other way alongside the engine and gearbox in a similar arrangement to the Lamborghini Countach and Diablo.
The result is a VERY quick car for the 1980s - 0-60 for early DMC-12s with this engine were about six seconds flat, with later cars making the sprint is as little as 5.6 seconds.