You need to know how far the pistons are down in the cyclinder at TDC and the volume of the heads you are using before you can calculate what you need in the way of chamber cc's to get to your compression goal.
For example: Assuming the block is at a nominal 9.600" then the KB107 pistons will be 0.012" in the hole. Assuming the your J heads have a typical 72cc volume. This will give you 9.36:1 compression with atypical 0.039 thick by 4.150 bore head gasket. Reducing the head gasket to 0.028" thick and you will have a 9.60:1 compression.
But you need to measure the head volume and measure the piston depth in the cylinder because most blocks are taller than the 9.6" nominal and the heads could be less or more.