Just replace the lifters then. The reason why there's no point in building up a strong bottom end, (pistons, rods, crank) and not spending money on the heads/cam/intake, is that the heads/cam is where your motor makes hp. It's what controls how much air goes into the motor. If you put a stock heads/cam on a 383 bottom end you will still be making stock hp naturally aspirated. Do some reasearch on heads/cam options and engine buildups on www.camaroz28.com