GM calls that part a Dampener.

 

Some other LS series engines have a chain tensioners(dampers) in this location. It is a solid piece mounted in the same location bolting to the same two bolts seen in the photo. It pushes out on the chain from the inside from both sides rather than pushing out on one side and in on the other as this one appers to do. If your block is drilled and tapped for these two bolts you should probably be able to use either one of them. Maybe this is the new improved version.

 

The LS2 style Dampener bolts in between the cam and crank sprockets. It pushes outward
<---> on the inside of the chain. GM part number 12588670.