Away from home so cannot go measure my collection of pistons. But generally there is a difference in the piston crown in the dish. In my case I measured the volume of the head I am using, head gasket size and then had the pistons made to match the compression ratio and head and squish band required. If you are looking for something non standard you will likely have to do something similar.
There are a few engine builders you can get support from in this regard.