With a 1.5" level you should be just fine! If you don't want to f-with lifting up the front, you should have 1.25" blocks in the rear, could always take those out.
I had the 2" Rough Country level...not a terrible ride, it makes NO difference unless you chage springs in the ride. The ONLY difference would be bouncing off the metal bump stops on rebound...which is what feels like a stiffer ride. I HATED that aspect of the level kit...which is why I ended up going with a full suspension system.
Body lifts are also an option for the GMT900s