Pistons specs question for 340 build

The -5cc pistons are likely flattops with a five ccdeep valve relief. The -16cc are likely dished. You will need to have the compression height of the pisons (measurement from center of piston pin to the flat part of the piston head) to have a vague idea of c.r.
There are a bunch of ACTUAL measurements that need to be done to get an accurate c.r.

This is incorrect. You have this backwards, as does "wherever" you found it. Let me give you these two examples off the top of my head. 351C ford.

KB148 shows a POSITIVE volume number since its dish ADDS TO the total chamber volume.

KB Automotive Hyper - Ford 351 / 5.8 - KB148

KB149 on the other hand shows a NEGATIVE volume number since it has a dome and REMOVES total chamber volume.

KB Automotive Hyper - Ford 351 / 5.8 - KB149

Care needs to be taken when talking about this stuff, because BIG mistakes can be made. lol