LOOKIN FOR PISTONS (318)

I'd use the KB"s at zero deck as racerdan mentioned and use the head gasket thickness to adjust the appropriate compression #. If your keeping the stock heads, try to find a cam in the 212-218 @ .050 range depending on your rear gear and torque converter choice. I hope the intake in that box is a Performer? that's really all you'll need.
I agree. The KB 167 would be a good choice if retaining the stock stroke.