well the LLY and LBZ in 06 and 07 are the same block just the computer is tuned differant. i have a LLY 06 but it has the LBZ tune from the local dealer. LLY has 310 hp and the LBZ has 360hp stock. i like my LLY been a great motor. im getting like 27 high empty and 23 city and i tow at 15 mpg. this is hand calulated. plus i do have alot of upgrades on my truck too. the truck is in my sig. i would go with the LBZ motor though more HP. but check around get the best deal. member its a buyer market dealer are high but deall them down they need that sale. good luck and ask any question you need for the truck that your looking at. you can find them out there too. there a guy here in michigan right now that asking $17,500 for a 2001 shorty crew cab. way high for the year. do a nada book value on them. plus make sure you get a carfax report there alot of them out there that were totaled and they rebiult them.