For budget or stock-style rebuilds, it's hard to beat the value of Sealed Power cast pistons. They are made from high-quality aluminum alloys and feature a carefully controlled casting, heat-treating, and CNC-machining process. And, because they're designed and manufactured to exceed OEM specs, they'll provide improved reliability, performance, and a long service life. (1979-1990) AMC, Jeep 258 CI 4.2L inline 6 cylinder cast piston. 3.75 Bore, 5/64-3/16 rings, .931 pin Dia.