1998 Venture oversize pistons

[skrea123]

GM SPO released a new polymer coated piston and rod assembly in 2003 to be used in any piston or rod replacement situation for the 1997-2003 Venture, 1999-2003 Monte Carlo, 2000-2003 Impala and many other cars with 3.4L engine. This new part has the GM number #12578021.

I'm about to rebuild my engine and found that is was out of cylinder bore specification and will for that resason mill it to an oversize, possibly +0.5 mm!

I have searched for an equivalent oversize piston/rod assembly but no retailer seems to know anything in Sweden were I live!

However if I search the internet parts dealer online catalogues there is another piston for the same 3.4L engine on article number #12578023!

Is it resonable to expect that #12578021 is std size and #12578023 is oversize?, GM used the logic in putting article numbers next to each other for such parts before!

If anyone have access to information finding this out, please help!

I'm keen on using improved parts rather than the original, particularly when the old piston had short and weak skirts that slaps for minutes after the start!