The stage 1 and stage 2 offcenter blocks are cast from the same casting. The only differences are the machining. The stage 1 uses production oiling to the lifters, which means the main oil gallery intersects the lifter bores. The stage 2 oiling is does not do this and small oil holes 1/8" are used to feed the lifters that you must drill and plug the other side from the lifter valley. The stage 1 uses nodular iron 2 bolt caps. The oil pickup is in a different location on the stage blocks also due to the 4 bolt mains. Stage 1 and 2 blocks with 3.8L are more prone to cracking between the frost plugs for some reason.