my 340..3 cars, 34 years, 1 family. where to go from here

Those may help with weight, but they are steel limiters to control piston skirt expansion.
Better cast pistons will have them.
OEM 340 (low/high comp) pistons were all cast pistons, no forged used.

im sorry, but i know that stock high compression 340's had forged trw pistons in them.