I went with Denny's Driveshafts when I had one made for my Monte Carlo SS:
http://www.dennysdriveshaft.com/ They'll give you specific instructions for measuring your truck so that you get the correct length.
Their prices aren't real cheap, but if you get their heavy-duty driveshaft, they'll replace it if you ever twist or break it. Seems like a pretty good guarantee to me. Of course if you're putting down enough power to twist it, I dunno that you'd want to put an identical one back in.....
