04 Denali Service Ride Control - Rear shocks springs etc..

[lil754boy]

I have a 04 with the Service Ride Control light on. I would like replace and want to know my options. I don't care about the factory system and probably would spring to ditch. I do tow cars often and also use as my family mobile. now the rear does way down when i connect my car hauler. I would like to replace and not have it sag so much but i also would like comfort for long distance travel.

I have seen something in reference to Z71 springs, Bilstein shocks?

What vehicle has the setup i need if any?