Directly quoted from Paeco's website
CHOOSING PISTONS
Making Custom Pistons:
Contrary to popular opinion, it really doesn’t cost any more to make up a set of custom pistons than it does to make up listed pistons. However, it is a little more troublesome, and we will need help from you on this in the form of three items:
1. An old stock piston . 2. A mold of a combustion chamber (or two molds if the engine uses mirror image chambers) 3. The cc volume of the combustion chamber.
If you don’t know how to make the mold or measure the cc volume, call us and we will walk you through it. If you prefer that we make the mold and cc the chamber, ship the head to us and we will do it for you. There is no extra charge for this.
BTW,, the price for a set of Ferrari pistons
Ferrari 308, 328 $960
I didn't just pull the numbers out of my a$$. This company has been in business for decades.