Before you buy pistons, first you are going to want to make a firm decision on 2 things.
What is the maximum amount of Horsepower you hope to make with this engine?
What type of Fuels do you plan on using?
These two questions will determine things like Compression Ratio, Wrist Pin Wall Thickness, Material that will help narrow your piston selection to a smaller set to decide from.
To learn more about how piston attributes influence piston selection, click here to read the Piston section of Jay's Bottom End Buyers Guide...