Engine block for an internal combustion engine

An engine block having machined front and rear faces, wherein each of the front and rear faces is capable of receiving and sealing against a housing enclosing a gear train for coupling the engine crankshaft to a camshaft of the engines, and wherein the front face is additionally capable of directly mating with and sealing against an engine front cover and the rear face is additionally capable of directly mating with and sealing against a flywheel housing, whereby the same engine block may be selectively assembled into an engine having one of a front mounted and a rear mounted camshaft gear train, wherein each cover and housing has a plurality of holes in predetermined positions, machined sealing surfaces on the front and rear faces have a plurality of holes in predetermined positions, there being sufficient numbers of holes on the front and rear faces of the block to align with all the holes of the covers and housings, said block further comprising fastening elements received in said holes, whereby there are redundant holes in any selected camshaft gear train configuration.