The knuckles are forged. Why do you want to weld the steering arm to the knuckle? You can bolt any manner of steering arm to the knuckle and doing that will be a stronger arrangement than trying weld to the knuckle. At least that way the steering arm is your only concern.
Swapping Mopar knuckles from side to side accomplishes nothing other than moving the brake calipers, it’s done all the time for that purpose and it doesn’t change the geometry at all. Flipping the steering arms is all that’s necessary, but as you’ve already pointed out unless you alter the geometry of them significantly the Ackerman is lousy. Less of a concern for a drag race only ride, but still a concern.