Walking through tractor supply I see there tractor section for shafts. They have a nice selection of yokes and all, and some of there biggest shafts kinda look borderline for a truck, maybe a street sissy front shaft or something, or strictly a spare to get you to the trailer. Just thought I would put this out there. I wont be trying it out, but someone trying to save a lil money, could atleast check it out. They would be super easy to build straight and prolly vibration free, becuase the shafts they have fit into the yokes. Didn't look too hard, but It looked like atleast .125 tubing, probably thicker. Seems like it was welded tubing though, again I didn't pay too much attention.

 

I have heard of people using tractor shafts before. They are fairly strong, I know the one behind our Kubota has taken a BEATING. If you search around here, Im sure you can find a guy or two who have used them.