From what little I know of high-end pistons for gas engines, one step up is "hyper-eutectic alloy" aluminum casting. There are forged aluminum pistons, but I don't know if that process is the same as forging steel, i.e. beating it into a mold w/ a hammer. While stronger, a disadvantage of forged aluminum pistons is that they expand more with temperature, so must be looser in the bore when cold and thus give more "piston slap" sound. They are thus better for race cars than daily drivers.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans