Paul Schwengel,
Welcome to the Stovebolt. I don't have one of these rigs so the SOP just might be big biceps. My first thought would be a worn out steering box.
If someone just did the king pins, then they probably looked at, or adjusted the box! Did you check it for lube and does it have any free play. If adjusted incorrectly, in an effort to tighten it up, it could be binding as it comes across 'center'.
Stuart
