Can I swap one set of .030 over pistons for another, without machine work?

A cheap **** would at least weight the new pistons and compare them to the old to get that variable taken care of. Did it feel balanced when you last ran it? If so, you could get away with at least getting all the new pistons down to factory weight. take weight out under pin at meatiest part of piston, or get lighter pins. Not the pro way but we are not all made of money.