from the latest info it will based on the same design as the new 4.5L Duramax also known as the LMK
there have been rumors of GM making it into a 6.9L or even making it a I6 Diesel but from more reliable info that i have found they are just redoing the 6.6L they now have..
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Late Nights=04 Chevy LLY Reg Cab 2500HD,its lite and fast
Business Truck=06 GMC LBZ 2500 CC SB SRW,Custom Tuned
Weekend Warrior=1987 Chevy Silverado RC LB 2500,lifted with lots of extras
Economy Saver=02 VW Jetta TDI,Stock for now