Mel or Steve -
Please take a look at this truck.
http://6066gmcclub.com/forum/showthread.php?t=47666
It has 8 hole wheels and definitely a Dana rear. You might want to look at your truck to see if you have one of those in there now. If you do, then all you might need would be a gear swap. If not, then this could be the rear you might want to look for, because it would be the right width.
Ray