Are the pre 99 and 99-02 rear springs interchangable? My dad is selling his truck and has a 6" lift rear spring that I'd like to swap him for my stocker and block. I tried searching and popped up with no help. I currently have the stock spring, a 4" block and what appears to be another 2" block. From what I recall, that's a big no no if you do any wheelin.