You are going to have to have one either custom made or at least shorten one to the correct length. It is impossible to find one that is going to be the exact fit for your specific engine and trans combo. There are just too many variables. With that said, you will want a HD driveshaft. If you need the mount for the HD carrier bearing, I make those.
http://67-72chevytrucks.com/vboard/s...d.php?t=620312