Bunch of Noob question from a Dutchman
The regular Performer is a good intake, but I consider it basically a stock replacement. I think I remember dyno tests, and it only picked up a few HP over stock. It does shave some weight though. The 750 Cfm carb size is good, given the higher gears and lower stall you will be running. If you go to a 24-2600 rpm stall, I would personally up the cam into the 230ish @.050" range. The duration of the cam you list is very low, it must be more of an Rv/truck grind. I have a very small cam in my 383, and it is 224/234 degrees, and you barely notice it at idle.
Unless you want to spend more money, I being a cheapskate would just try to find a stock cast replacement piston for the late 60's engines. One of the Hypereutectics wouldn't break the bank either. At the lower rpms you will be turning, I don't see the benefit of an expensive piston. I think you will end up in the 9 to 1 compression range utilizing the earlier piston with your open chamber cylinder heads, which will work well on pump gas.