Panhard bar. Used in the coil suspended 1/2 and 3/4 ton trucks. Was used to keep that rear end from moving side to side. The trailing arms would keep it from "wrapping" up under load. Look a bit like this?
http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=682734&d=1295146476
Was a common thing on the coil suspended trucks.


Steve H