For a street piston, these may work well for you. Hypereutectic with a deck height of 1.840 will put you .018 above deck, which will help with your open chamber heads. Relatively inexpensive at $390 amazon/$409 cnc motorsports.
Negative is the thicker 5/64th ring pack, but what your 340 originally came with, and they ran well
Keith Black Pistons KB243-060 Fits SB Chrysler 340 Flat Top 6cc Bore 4.100