One of the guys I wheel with runs a square tube front shaft. He's a crazy old fart who has only been wheelin for thirty years so I wouldn't put much stock in what he does.
Looks like a pretty good/cheap way to get a front DL. As long as you aren't driving Baja balance isn't a problem. Couple 'o u-joints and some square tube and away you go. The only thing I'd do is add a zirt fitting on each flat to lube it up.
You need 2.5 inch trailer hitch square tubing(trailer hitch tubing has no seam in it)and some 2 x 2 inch tubing for the inner.Then you go to Driveline service and get the weld in yoke ends for the u-joints and some new u-joints.Assemble (there are a few tricks to getting them to run true) weld them with a 220volt mig.I have built three fronts and other than being noisey when the t-case was disengauged and the hubs locked in they work great.(my rock buggy has one right now)The last one cost me about $60-70bucks in metal and yokes and about 10 minutes to weld.
what rockape said but I used the yokes off of my stock d-line to make mine. easy to do just a little time consuming cutting the yokes off the original d-line. take your time squaring the yokes up the best you can with the sq. tube. I've heard of people taking their square d-lines up to 50-55 mph, though mine is just a trail spare.