In the old AP catalogue it is stated that you must now mix those AP Formula / HD parts with std items. Also the difference between the CP5351-1 and the CP5352-5 is that the 51-1 is steel-backed and the 52-5 is not. The 51-1 islisted as for the Pinto engine, the 52-5 for the RS1800. Torque capacity is the same for both.