Say I wanted to use the KA24DE tranny, what would I have to do to make a driveshaft that fits.

Warning: I have not personally done this, but...

You can use the front section of a S13 (240SX) driveshaft mated to your current rear section. The S13 front section will have the correct yoke for the trans and will bolt up to the S12's rear section with no problem. If you go to the junkyard to get the front section you'll need to be prepared for two things. First, you might find that most if not all the manual trans S13s there already have their drivetrains missing. Thats the problem I had. Second, check and see if your carriage bearing is on the front or rear section of your driveshaft. It should be the front but I've never gotten a difinitive answer for MKI vs MKII drivetrains. I know that some S13s have the carriage bearing on the rear section instead of the front. I have gotten no feedback on this fact but I can say in certainty that there was at the very least one 240sx in the universe that had its bearing on the rear and unfortunetly I found it, removed it, and purchased it without knowing I had the wrong part. My car is a MKI and yours is a MKII fyi.

OR....

Install your engine and trans and call up a good shop that makes/repairs driveshafts and such. They'll tell you how to measure for it and then they can make you a custom 1 piece driveshaft. Thats what I have under my car right now. Very happy with it. Be sure to tell them that even though the car is a 200sx the trans is from a 240sx and they'll get the right yoke for it.

Link of my trans conversion including info on driveshaft and pic of my new 1 piece.
If you go with the S13 front section option then be sure to properly phase the U-joints. Its covered there.
http://www.club-s12.org/forums/index.php?a...=11&t=18215

Link for the driveshaft shop I used. They're based in Las Vegas but they ship all over the world with no problems. But if you have a good local shop then I would keep it local. I paid just under 300 bucks for my 1 piece btw.
http://www.drivetrain.com/

And..
http://www.driveshaftshop.com/


Damn it took me forever to write this reply, lol.

heh, long reply, but it was nicely written and answered all the questions I had.

Also, we dont have much in the way of car shops around here, just repair shops, closest one would be in chicago, and that'd be hell to get to, my corolla has alignment issues....anything over 65 lately and it shakes like hell.

I looked at the driveshaftshop earlier cause i think i saw the pic of yours with the sticker on it for their site, seems good, but i'd have to contact them and things. Ill have to look at drivetrain.com though, as long as I can call them up and explain what i need, it will work out.

I think the pic you saw was in this thread ( http://www.club-s12.org/forums/index.php?showtopic=13929 ). A killer build and unfortunetly not mine, hehe.

good luck