[quote=Michael Ecks]As already stated it is a late 360 balancer. Not sure what year, but at some point the engineers realized they could remove the old style eccentric weight and hollow out the same amount of material from the opposite side of the outer ring and have the same balancing effect while reducing rotating weight. So, your part is "good-er" for that engine.

I wouldn't agree the "scalloped" dampeners are "good-er" for any level of a performance build. The imbalance is moved outside of the elastomer bond, placing more stress on it, and they are prone to the outer ring walking around when used on engines that see much use over 5000rpm, especially as the dampener ages and the elastomer deteriorates. The style with the counterweight cast on as part of the center hub doesn't have that issue, and will keep the outer ring in place in the event of elastomer failure. So while the scalloped dampener may reduce reciprocating weight, IMO it is the poorer choice in the long run - both reliability and safety wise.

In some ways this is a moot point, because a performance build should be running some level of an aftermarket performance dampener.