With addition of batteries for bursts of power, 50 kilowatts should be adequate for a car. That’s about 70 HP all the time, a standard engine is made to run continously at about 1/4 of peak HP. Assuming a decent battery pack, 50 kw power source should perform about the same as a good sized v-6 engine.
I was allowing a little extra for oomph on acceleration, as well as some loss from translation of the heat energy to vehicle motion.