Cummins makes many differnet fan hub setups. Some can be turned upside down to provide for high mount or low mount fans. They can be mounted on the head or the block. All Cummins fan hubs, except the Dodge, have a conventional 4 bolt mount, usually 8mm on a 50mm bolt circle for "B" engines, for the fan itself instead of the lefthand thread like our trucks have. Some have a "square" mounting pattern others a "flared" pattern. Shadrach