you are right on crackedback, originally had the 1068 on it, switched over to the 1085 witch is a little shorter, I have a 51515 on the shelf but I don't think it will fit, I had a tough time getting the 1068 off with the TTi's, things are so tight on this, the reason why I went to the 1085, we have TTI step headers with a canton billet oil filter adaptor plate.