i "think"the k727 joint has a bigger taper than the k781/783 joints, as it fits the imperial from 59-66, and those take the k778upper joint that is also common to the 74-78 c bodies and 1/2 ton trucks, which have a bigger taper than the 62-74 b&e joints. the lower screw in joint that has the same taper as the 62-74 b&e bodies is the k719. however, that screw in joint has the same threads as the upper ball joints, so it won't screw into the lower control arms that take the k727 joints because the body thread size is smaller. hope that makes it clear[as mud].........