Randy,
I have a one piece in my '71 SWB and the same thing happened to mine. Except it dinged it up enough to cause quite a vibration...yikes! Has yours gotten dinged up at all???
Apparently, when the PO swapped the engine and trans in my truck, he also swapped the shaft...which was a 3" OD (and thus didn't have enough travel/clearance at the crossmember). It was very 'tight' and you could hear it 'ping' sometimes just dropping it into 'drive' (and 'reverse')....ARRRGGGGHHHH!!!!!!!!!!
Here's the thread (which piper may find useful too):
http://67-72chevytrucks.com/vboard/s...threadid=67673
If I had a longbed I would probably go with the 2 piece setup....after discussing driveshaft workings, travel, ect. with my driveline guy. He said anything over 6" is "tricky" when it come to single-unit shafts. "Whip", and clearance, seems to be the issue, according to him anyway........