that linkage does some wacky things as the wheels move around- you'd have to spend some serious time redesigning how it works to get a rack in there. First problem is that the rack would have to move about 2 feet!

But I agree with the below posts about parts replacement, and have another thought:
Alignment is a big factor in steering feel.
As long as the issue isn't STOPPED turning (which you just shouldn't do anyway, ps or no) then have alignment checked.
If it's right, you can have the car re-aligned with a lower amount of caster, and make sure it has little (or no) camber. You might have a hard time finding someeonee to do this, but reducing camber will reduce both effort and self- straightening. Be careful- too little makes the steering too light, or can even make the car self- steer. But the factory values do make for pretty heavy steering (on my car).
Also, make sure the wheels are correct- too much offset also loads up the steering.
Another thought,
t

If you haven't done so, you should also be sure everything in the current system is in good order. Years ago I had a 122 with stiff steering, then had the lower ball joint fall apart in the middle of the road. The steering will always be harder than newer cars, but a rusty and failing ball joint makes it tougher still and is not a thing to ignore.

Perhaps just going over the basics of driving a non-power steering car with her might help. Which just entail never trying to turn the wheel with the car fully stopped. Inching it slowly along as you turn reduces the effort tremendously. Pumping up the tire pressure slightly helps too (make sure you keep the rear slightly higher than the fronts to maintain safe understeer).

If the steering is stiff while moving you might have a dry steering box or some stiff ball joints.

The geometry of the steering linkages is not conducive to tinkering. On my 544 I tried swapping to left and right arms from the hubs because they had a very slight curve on them and I needed a little clearance for some wider wheels I had. Tried driving it once and it worked well straight ahead, but once the wheel was turned it would pull hard to lock and really scrub the two front tires against each other. I put it all back to normal and got some different wheels.

I understand that there is at least one Toyota whose power steering box
will bolt in. The one from the 164 is quite a bit too big to fit or bolt
up. In any case you'll probably have to fabricate a hybrid pittman arm.
I don't think a rack and pinion steering gear will work in a 122, and even
if you could get one to work there may be serious ground clearance issues.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

Paul,

I don't think that any of the 122s came with power steering from the factory, at least not those that were exported to the U.S. It might be possible to retrofit the pump and rack from a 140/164/1800, but you'd probably have issues with regard to mounting the rack.

This is all speculation on my part, since no one else has responded at this point. Hopefully someone can shed some more light on this...