Late (74 only as far as I can tell) 140's had power steering, based on the 164 pieces. Depending on what revision of Haynes manual you get, there *should* be details about that. There was a car on ebay, which was a 73 145, that the owner had retrofitted power steering to.
So it's possible. With a factory wheel and a steering wheel wrap that fits my hands, I've never had a problem with too heavy of streering, even with 195 tires. Possibly check out whether your car has atypically heavy steering due to wear or alignment problems.
Or if you like to modify and have the equipment- taps, welder, easy access to 164 parts in useable condition, go for it. It will be a very rare feature.