Depending on the length a single piece driveshaft may be unsafe and unsuitable.
They can only be so long and not flex and fly apart, that's why they use multiple shafts on longer trucks. Thicker wall and larger diameter can allow a longer shaft to a point... there are a lot of variables, before just deciding you want a single piece driveshaft consult with a reputable driveshaft builder and see if they can make one to work in your application.
Or you can read the manuals and get a pretty good idea yourself.
http://www.stovebolt.com/techtips/driveline/setup/index.htmlGrigg
