im trying to figure out which pistons to get for my 355 build....what is the difference between these pistons. i have no idea what they mean... i will be using afr 180 heads and the gm hot cam with my ported aftermarket TPI setup... which one of these would be best.. this engine will be mostly a fun street car with the occasional strip life.... i want to get all forged internals because i will most likely be using nitrous at some point.....

Flat top, with two valve reliefs,
Dish, with a D-shaped cup,
Flat top, with four valve reliefs,
Dish, with two valve reliefs,
Dome, with two valve reliefs
also what does piston head volume mean... summit gives these sizes..... which ones should i go with
5.00cc,
+24.00cc,
+6.10cc,
+4.00cc,
+22.00cc,
-11.00cc,
+20.00cc,
+13.80cc,
+12.00cc,
+5.40cc
basically i need help because i have no idea which rotating kit to get.... if someone could point me to a complete forged kit to work with my combo that would be great.....

 

You are opening quite a big can of worms with your piston question. My first suggestion is do not buy any parts yet. Get your entire build organized on paper before you buy a single part. Know how much you want to spend before you start. Power costs money. Lots of power costs lots of money. Once you change one major thing on a tpi motor you will have to buy/change a bunch of other parts to keep everything in balance. Search this site for opinions about which parts to get.
I assume you are going to be using a machine shop to machine a block for you. A reputable shop will be able to give you information on relating what size head (combustion chamber size) to get in regards to which piston in order to get a usable compression ratio. The machine shop will help you pick the right parts. Of course you can teach yourself most of this from searching this site and the net and reading magazines/books on this subject.
A few other questions you could be asking yourself before you start are; what am I going to be doing for computer programming, what injector size will I need ( this is going to depend on whether you are going with a wet or dry nitrous setup),do I want a different throttle body size,do I want to build a 355 or a 383 (ie is fuel economy/power or ultimate power your goal etc.) Each decision you make can effect previous decisions (if you go with a 383 you may want a bigger head than a 180cc and you may find a ported tpi setup will limit your rpm/horsepower too much).
As I said, a big can of worms. You probably have most of this worked out. Take the time to get it all right. People on this site will be a lot of help.

 

Are the 180 heads aluminum or cast iron? It will make a difference in how high of a compression you may want to run, especially on pump gas. What are your plans for the car? Is it going to be a daily driver, where you may end up getting bad gas and blow up the motor again if your compression is two high. These are all questions that you have to ask yourself.
The piston head volume is going to help in calculating your static compression ratio, but that's isn't all you have to consider. Compression distance and a good quench are also things you have to think about. What material your pistons are made up of is another factor, which will also depend on your application. I had to go through a similar situation almost a year ago and I must say that the people on this site have been very helpful. However, you still need to do your homework and figure out what it is that you want to do, because no one can figure that out for you.