You did your 4x swap. This question is not to insult you,but do you know what caster is,and what things can change it?. I ask because if you were unaware that the rotation of the front axle beam relative to the frame is critical. If the front axle beam is rotated it will affect caster. Things like are the spring mounts on the right location,right height,etc. If you look at the front wheels on a grocery cart the way they trail when you push the cart. That is caster. Without that trailing effect the wheels would go every which way..
