While doing the headwork and replacing the base gasket, why not a set of fine quality forged pistons that are significantly lighter? Retain stock bore and just replace the pistons and rings. Is that cost effective? I would think so, if you can reduce reciprocating mass in the pistons, would not the engine rev a tad quicker?
Would there be a clearance issue as forged expands more cast?......in other words, would the forged alloy pistons have to have more of a cylinder wall to piston clearance? If so, how much more with a stock bore?.