Hi there bad_andy, I have Ross forged pistons in my supercharged a14 and the can (reportedly) handle up to 25psi of boost.
Ross is an american company and they do custom jobs for reasonable prices ($AUS1400), which included everything that a piston kit normally includes...

If you go forgies, get the compression sorted first- I am not a big fan of using head shims to decrease the compression ratio

the easyest way is to stick a shim under the
head to drop the comp.The shim is an off the shelf item.

this site is one, there are a few people on this site with turbo a series and a couple supercharged i'm sure they could steer you in the right direction

Depending on the setup I might go up to 14lbs. I'd want to run an electronic boost controler of some type if I can with the application. So if I do, would you recommend changing any other internals. (Where can I get forged A12 pistons?)

Also, does anyone know of a good site for turboing an A12.

Depends on how boost happy your gonna get . 12 and under cast is fine , but if you really want to boost hard go for forged ones.

If I was going to go turbo, I would be rebuilding the motor anyways. So, I mean would it be worth the money to go with forged pistons and other stronger parts, or can the stock equipment handle like a stage two turbo setup (intercooler, lower-mid boost).

There's no list ... anything that is done to a Chevy V8, for example, can be done to the A12. All the things you mentioned, plus more. But it's less expensive to swap an A15 in (25% bigger to start with).

For turbocharging, nothing needs to be done to the engine internals. There are several turbo'd A12s with stock block and heads.

Does anyone have like a list of things you can do to a stock 1200 motor to build it for power? Like what compression, what headwork, what carbs, etc.

Also, does anyone know what turbos can be used with the A12 and what work should be done to the motor (forged pistons, etc.) before turbocharging it. I know people who can machine/fab up the parts.