Remember though that the reason USA Panteras were limited to around 2° was because of a steering effort consideration by FORD. As you go more, you progressively increase the steering efforts.
While some here say that isn't a problem for them, the perceived market customer of maybe an upgraded secretaries car, like the original Mustang, would not be able to either handle or LIKE more effort.
The emergence of the EPS for these cars has raised the interest of arriving more to something like 6°. That's why there is discussion of increasing positive castor in the Pantera.
For the moment, center the ball joint bolts in the slots. That's going to be pretty close to the negative camber that you will want in the front.
Camber locks for street cars were never a high priority for Panteras regardless of the perceived short comings of the design.
To do them correctly, you really need to remove the upper arms and do the modification on the bench, not on the car.