Adding a main girdle to your Duramax is one of the most popular durability upgrades on the market. Unfortunately, anytime you add height the oil pan rail it causes bolt misalignment at the rear cover. The only correct way to accommodate this change in height is to relocate the threaded holes in the upper oil pan. These T6061 aluminum bungs are threaded to match the rear cover hardware and are designed to be welded to the upper oil pan after assembled height is determined.
All high level DHD engine builds utilizing a girdle, leave the engine room with these bungs correctly located in the upper oil pan.