Smallblock Pistons: 1 question.....KB's -or- Sealed Power(SpeedPro hypers)???

Which ever type piston you choose, all things being equal isn't going to dictate how fast the car goes. Just durability. I say build the bottom end strong and it will handle anything you throw at it in the future. There gonna want to go faster eventually, and you wouldn't want the short block to be a hindrance. Control the ET with the top end or gear.