Hinson Supercars makes a conversion kit for the 240. If you look through this forum, you will find a lot of people who have done, or are working on this swap into both the S13 and S14 chassis. They have each taken a somewhat unique approach to the conversion in the way of motor/transmission mounts, cross members, exhaust, cooling, wiring, etc. The iron block will work, although you get 90 lbs of additional weight over the front wheels. The KA motor is slightly lighter than the LS1, so the chassis maintains a similar balance. There is also some question as to whether the F Body or Y Body front accessories will bolt up to the LQ4, since the truck accessories will not work under the stock hood, and may also have clearance problems between the engine and radiator. If there is a choice, the LS1/LS6/LS2 is the way to go.
Good Luck!