I've salvaged two force balancer/oil pump assemblies for the '88 duke.
Used to be near impossible to find. And Rodney Dickman is the only guy that has new ones, and those are about $200 shipped.
I'm willing to sell each at $75. One was from a GM replacement crate motor made in 1997. One is from a motor that had sat in an auto shop classroom. Both motors had sat long to rust beyond any other reasonable salvage.