4933S tuning kit

My 70, 340 is .020 over but otherwise a stock engine. I have rebuilt the original 4933S Carter but feel a good tune would benefit the performance. I am having a hard time finding a tuning kit with the 3 step metering rods and would like to keep the domed caps for originality. Does anyone have a good part number or source for the correct rods, jets and springs?
Thank you, Jerry