The bigger difftween earliers and later engines is the compression rate. Factory lowered down with lower pistons. The correct way to bump up would be then get the correct pistons.

Then you can choose the camshaft, HP exhaust manifolds, windage tray, valve springs. But need to bump up the compression rate.

The cheaper and cost efective for this is KeithBlack pistons. They have two for 440, one flat top, and one with quench step. On $400 rate

You can also get closed heads as mentioned, but that could be more expensive than the pistons ( $1000 rate ), althought easier to bump out the compression rate and to work. If you can build the engine by yourself, the pistons will be cheaper and still the correct way. Since 69 all engines where open chamber heads, so you can live with the heads you have. Maybe mill down a bit will help a bit more. Get metallic headgaskets.

After get the pistons, you still can get closed chamber heads depending on which pistons you get and how they fit into the block, block height, headgasket used etc... but pistons first.