before you get flamed, ill jump in. those are called triple mikuni carbs. do a search on those and you should come up with plenty of information. just know, carbs are a whole diff animal than efi.
check out other forums such as 240sxforums.com and nicoclub.com . they have rb forums and you can see what a clean swap should look like. also find vids on streetfire.net youtube.com and video.google.com of running rb25 240sxs. those should give u and idea of what to look for. hope that helped and good luck with the car:burnout:
i think its a good idea to get the 240sx b/c once the rb is removed from the 240 u have a shell u can sell to a drifter who wants to swap in an engine. definitely go for the 240 if the rb25 is running.