Ok. I am helping my son build a D16Z6 for use with a turbo. He bought this motor all machined and ready to build. The pistons say 0.50 on top of them. I am assuming this is 0.50 over bore, but I am an old Chevy race motor builder and new to the import sport. He has been told he has to buy a $150 head gasket for the bigger pistons. We never had to buy a different head gasket back in the old days. Is this true or is someone just telling him this because it is their opinion? I want to build this thing right, but I don't want to spend money where we don't have to either. I know the block has been bored, and decked. Any help would be appreciated. I am an old guy trying to help my young import loving son. Thanks for any info.