The 4x2 needs a 2.5" kit.
The 4x4 needs a 2" kit.
Go here:
http://www.prgproducts.com/shop/prod..._leveling_kit/
Tell Greg that Blackbeauty sent you... You won't be sorry.
Oh, and the 1.3" kit is for the '08 Titans that come more level from the factory.