A stock ball joint has a plastic sleeve around the steel stud at the slot. When you reach the end of travel of the BJ, this plastic sleeve acts as a bumper to soften the hard stop.
A lowered BJ is exactly the same as the stock one, but with this plastic sleeve removed.
Get stock ones. Then if you are so low that you hit the sleeve, take it out.
FYI, it is possible to set the front beam on the ground and still not reach the end of travel of a stock BJ, depending on the diameter of your front tires.