You could call the dealership and see if there is a stock kit for a lower suspension, but considering the weight of a casket and corpse (assuming you use the Suburban as a hearse) you may want to go with an adjustable airbag kit instead. Most local tire and suspension shops should be able to give you quotes on lowering your vehicle or installing the airbag system depending on how low you're wanting to go. Also, a friend of mine had a 3/4ton 97 suburban and put 1/2ton springs on it, the extra weight of the truck brought it down to a lower ride height but decreased the weight capacity as well.