No matter which block is chosen, it will be built for the 400hp range. I've heard that sr's can be laggy. Any particular cause? Don't get me wrong, I've seen a handful of decently built sr's but it's nothing that special because nearly everybody owns one who has a '40. A well built Ka-t isn't something seen at every car meet. I'm not saying that there aren't any Ka-t's out there in the Bay Area but they are far from few compared to the sr. The main reason why I chose ka over sr.