Chevy II  1966-67 L79 327 350 HP STANDARD PISTONS Corvette GM 3866954 Forged TRW. These forged pistons are made of aluminum alloy material. The set is a vintage part with the manufacturer part number 3866954. 11 to 1 compression. Nice shape. Need a good cleanup.SBC Small block chevy. 5 are stamped TRW 3866954 underneath, the other 3 have different numbers underneath but have 3866954 stamped on top. They are all exactly the same, but probably from a different TRW die.