is it possible to weld the stock U joints to square tubing in order to make a square drive shaft? I think they may be cast on my friend's toyota and we were going to try and make one of thease but we aren't sure if it's possible to weld to the stock U joints.. any info will help, thanks

You can make square tube driveshafts, but they're only for dedicated offroad-only slow moving rigs.  You can also use them for spare driveshafts.  The one I saw the guy had welded U-joint mounts to each end and had actually made it a two peice shaft so the thing collapsed in on itself to about 60% of it's max width.  It was just a spare but that way it took up less space.

You wouldn't want to use it for anything high speed, especially road use.  It'd vibrate like a mofo.  Square tube's gotta be about impossible to balance.

If you watch Xtreme 4x4, they made telescopic box tube drive shafts for the Cheep Jeep project they spun them off on the trail run, but it was the u-joint that broke.

thanks