1971 Demon Strange steering problem

AJ/FormS said
I think this is real simple; but the cure is not cheap.
I think it could be a combination of too much scrub radius and the lower control arms not set parallel to the ground-plane. Here's my thought;
the scrub radius is causing the tire to pivot and drive away from the centerline of the car. The effective length of the Lower control arm changes, allowing the camber to change, which allows the wheels to toe out, and all this monkey-motion cause the ride-height to change..
I have seen this several times with the powertrain out; when there is no weight to prevent the tiny force generated by the scrub radius to resist this action. Once the engine went in, this action seemed to quit, but that scrub radius problem was still there and could now be felt while driving, as a nervous twitch, and a wander. The only cure was to restore the scrub radius back as close to zero as possible.
If you don't know it, scrub radius is a point in the tires contact patch, created by an imaginary line drawn thru the upper and lower BJs, down to the floor; relative to the centerline of the tire, at the floor.

In the factory suspension engineering, this point is very close to zero, when:
the lower control arm is parallel to the ground,and
the camber is close to zero, and
the wheels have a Zero offset, and
the tire is of a specified height.
Changing any one of those changes the scrub-radius.
You have, I think, changed them all.

I simply don’t buy this at all.

First, in the factory geometry the lower control arms are not parallel to the ground. The difference in height between the LCA pivot and the lower ball joint is 1-7/8”, for the LCA to be parallel that number would be 0. While it’s hard to tell from just a picture, it doesn’t appear to me that the OP’s car is higher than factory. With the drop spindles that could be changing the lower control arm angle up from stock, as he doesn’t look 2” lowered, but I’ve run drop spindles without that issue.

Second, the ride height change he’s describing is 2”. Even if there was some validity to that scrub radius effect as you’re describing it, that change would be no where near 2”. The toe change required to do that would be massive. More likely the change in toe is following the change in ride height (not the other way around like you're describing), as the car lowers the LCA's get closer to parallel to the ground, making them effectively longer and because the tie rods stay the same length the rear steer set up causes the wheels toe out.

And finally, I run the same QA1 LCA’s, high offset wheels, more negative camber and more positive caster than the OP does without anything like the issues you describe.