that depends on which small block and which 6 cyl you're talking about. odd fire 231 (76-77) pistons would work with the 350, i'm not sure about the even fire 231 (78-87) ... with that split throw crank, i think the offset con-rods screw up the piston/pin but i'm not sure. pistons for the 225 would interchange with the 300 and 340. you might could call www.TAPerformance.com and ask them why they list a seperate part # for the NA 6 cyl.
