Good to know you are going with a 340 block to match up to the 340 carb.
One of the more tedious things we are having to do is bead blast all of the Engine components before they go to the Machine Shop. They usually Hot Tank everything but that process does not remove all of the corrosion. We want every piece to be like new so these parts are being scrutinized to the nth degree. Below is a picture of the Intake and Heads after being blasted. They have zero corrosion and are ready for paint. We will be using Spies Hecker (hardened) paint. It is so durable that it does not burn off or change color with heat like most paint products do.