I think there has been some confusion generated in this thread. There were heavy duty trucks that had 5 studs on the front and 10 on the back. The rims were centered by the hub and they had a round plate that went on the outside of the wheel. The lug nuts bolted up against the plate. This was for strength.
The GMT400 trucks (88-00) with dual wheels have a similar plate and mounting method, only with 8 lugs instead of the 5/10 pattern.
