Reply to "darty steering"

I would say you have a "toe out" situation.
With toe out one or both wheels are always steering.
So if you manage to get the car pointing straight ahead both front wheels are steering slightly outward.
So the slightest movement of the steering wheel, for example, to the left and the car will dart left & vice versa.
So you are forever trying to correct the direction.
Combine this with the Pantera's lack of caster and you have a car that does not want to self centre.
So you change lanes & have to physically pull the steering back into line.
Where as most modern cars will go back to a straight ahead position when you let go, or ease off steering wheel effort.
Then there is the built in bump steer.
If you have toe out & your steering wheel is slightly left of centre & the wheel hits a bump, it wants to steer itself.
So that just makes it worse, darting around.
So, a small amount of "toe in" keeps the car tracking straight.
There is a kit some of the vendors sell that slightly corrects the rack height which is part of the bump steer issue, (the main cause of the bump steer being the distance from rack end to rack end is around 2" to great).
And more caster, that requires a top arm modification to achieve.

The joys of 1970's suspension dynamics !

regards,
Tony.