That is the customer's problem. I would just showed them they gave you the wrong one to put on and you did not catch it before installing it. Show them the 2004 head vs the 2008 head. Let the customer deal with the place they bought their rebuilt head from and hopefully they can get a 2004 head in exchange of the 2008 head to put on there. The newer head gasket will make it leak faster it will be fully opened. I do not know if its possible to weld up that valley near the cylinder head bolt goes by to seal it up.