Thanks for your reply Keith.
I have checked for pistons, the one I found are $700-$800 from Ross Pistons.
Having the heads and intake milled is about $200.
I will need custom pushrods anyway, with the original ones lifter-preload is 0.080 at this moment.
If you've got another source for the pistons I would be glad to hear.
I don't think it is possible to change the pistons with the engine in the car?