I finally realized that your working on a 440 pick up truck motor, not a 400
Check on the prices to fix your heads and if it costs you more than $700.00 to $800.00 I would buy a new set of aluminum heads like the 440 Source brand or Eddy E heads for a little more money or maybe some of the other cheaper China import 440 aluminum heads
They will flow better and make more torque and HP and run better on todays pump fuel also
On the piston selection wait until you know which cylinder heads your going to use and the combustion chamber size and metal type, if you use new aluminum heads you can run more compression safely than you can with the same size combustion chambers with a iron head
Check with United machine on their Silvolite cast piston line for your rebuild. I would shoot for less than 9.5 to 1 compression ratio with iron heads and less than 10.5 to 1 with aluminum heads