Upgrade engine and pistons

I am going to try this here.

I am in the machine phase right now.

I am having my block cleaned and decked. Same with the head. I have the crank, rods and block being line honed. Cylinders are being honed. Camshaft is being ground to a more aggressive setup with new lifters/push rods.

I am eying a set of over sized valves and 318 springs.

My question is what valve cc should I shoot for? My other question is do I need to replace the pistons or will cast pistons handle the higher compression?