I went with a 62/65/13 because after talking with many turbo builders I was told it would be best for my application. I want quick spool and to be able to tow 10-15K on a regular basis, but still be in that 450+ range. They all would go back and forth about the ex housing. I heard both 12 and 14, so I went with the 13ss because in theory it should spool like a 12 and flow like a 14.