The RB25/26 both have a good 100lbs over the stock KA, which has about the same on the SR. Being that a 240 with an SR is an excellently balanced car, the RB in a 240 will make it push some, due to the extra 200lbs (appx.) up front. Also either stock KA springs or an adjustable coilover system should be used, due to the extra weight up front. This is only if you want to lower the stance.
Not bad, just some extra weight - not what everyone wants in a car.