I don't know much about the RS9000's but I personally wouldn't run them because without the in cab adjustment system you have to get out of the vehicle, contort yourself into the fenderwell or undercarriage of the vehicle and turn a knob on the end of a shock. I like to keep things simple. For the durability of the 9000's, but with no adjusting a knob, I'd go for the Rancho RSX's. The big burb shouldn't ride very rough with them, considering how heavy the older square body style burbs are. I too own a 1989 Sub and want to install a 4 inch kit, but am confused to what size tire I should run 33's or 35's?