This will most likely require removing the gas tank on Blazers and Subs. Pinion angle is a popular question with this kit. The quick and easy answer is that there is no quick and easy answer. Proper pinion angle depends on drivetrain length, wheelbase, gears, tires, vehicle speed and more. It usually boils down to what works for your truck.
Load carrying ability is also a common question.
Basically, if you keep the factory overloads, you won't have any trouble. 56 inch rear springs are not a problem for the flip kit. The first thing you will notice is that there's two different shackle flip brackets. Since the brackets are designed to move you shackle mounting point forward for the proper shackle angle. It is important that the brackets go on the correct side.