What are the differences? LOTS. About the only thing that is the same is the bore and stroke dimensions, the rod and journal sizes. Rings are interchangeable, but I prefer the newer piston design. Rods are interchangeable, but I like the bevel wrist pin design for the later models. No intermediate shaft in the ALH, but the water pump is in the timing belt circuit. The ALH oil pump is much better than the AHU gear style pump. AHU is a terrible spin on filter in a lousey place. The ALH has a drop in filter in a great place. Better vacuum pump on ALH, in my opinion. ALH Turbo is a VNT instead of the AHU wastegate. Virtually the same injectors, but ALH used higher pressures. There are a multitude of other changes. Many changes, like oil pan, valve cover, intake manifold, engine mounts. etc. cylinder head uses the same valves and lifter size, but different cam driver for the ALH vacuum pump. They are very different designs built on the same crank and block dimensions.
