What do I have (suspension)

[Nitrousbob]

The truck used to be a 2wd, the last owner converted it a while back
My end result is I want another 4" in height and a softer ride, its a 3/4 ton right now and I dont do any towing

Here is a couple pictures, It looks like 4" blocks in the back, and the front springs look almost flat across, i believe the front suspension was taken from a suburban?

I was looking into a tuff country 4" lift, I just dont know if the rear springs would be the right height if I just went to the 4x4 springs with 4" lift , same question with the front.

not to mention replacing the 2piece driveshaft