There may be a small amount of interference in the angles between bar ends and the a-arm brackets, making it difficult to attach all the bolts. In that case, you might need to jackstand the frame and use a floorjack under each a-arm to get the angles correct so the bolts go in unstressed. I find adding a spot of oil to the a-arm attach bolts helpful. Many Pantera body/chassis are twisted a bit- especially those with big wheels and stock bay-braces, making the angle-matching with swaybars even more problematic.