I found this MOS water block that might fit. It is 80mm long, 14mm wide and 16mm high. Keep in mind the hight is WITHOUT the connections.   So even though it is 80mm long, the block is only 16mm high so it will not stick out of the went hole. The connections will stick out and because the is closer together they might fit through the went hole.   Also the wide will not be a problem either.   Now the question, will the heat sink still transport enough