zc pistons in an a6

I have an oportunity to get a set of srp high compression pistons from for a d16zc, is it ok to put them inside my d16a6. The compression of the pistons in a zc is 10.5. What will it be in an a6? Do i have to worry about the valves hitting? They are used, is there anythin else i should know before purchasing them? Also if i raise the compression do i need to get special gaskets and head bolts?