If you look at any make of car from the early '70's, very few if any had electric fans. They were expensive & unreliable compared to today's sytems. A vast majority of cars on the road were, front engine- rear drive, like the 1200. It was dead cheap & easy to bolt the fan on the water pump & away we go.The next step was to mount the fan on a temperature sensitive hyfraulic clutch that was then bolted on to the water pump. Hot rad, hot airflow, clutch engaged, fan driven Cold rad cold airflow, clutch/fan freewheeled, less drag more power & economy. (Clutch fans are still very common on light & heavy trucks because of their durabilty.) The next setup is what we see on cars today. An electric fan is almost the only way to go on a front wheel drive car. The engine is sideways most of the time, so the water pump is pointing the wrong way to mount a fan. The new fans are very efficient, & when thermostatically controlled only run when needed.
When my mom's '73 1200 sedan was new my dad used to take the fan off completely for winter driving, which gave better performance & fuel mileage. (You must realise we live in Canada, where it's on the cold side in winter).I wouldn't recommend doing this to anyone now however. I think an electric fan conversion would be worth while if done properly. I'm sure many members on this site have already done so. I would think that the auto wreckers would be a good source for a cheap fan. A Honda Civic, or Nissan Sentra rad fan might work well. One can only guess, but I would immagine that a several HP increase would found, especially at higher RPM's.