from what everything I have seen, if you switch your rear axle over to a 14-bolt (had a 10-bolt on my K10 blazer before) you need to either change the driveshaft to fit the larger yoke on the 14-bolt, or get a combo u-joint that has a 1310 on one end and a 1350 on the other. From what I have heard, (and saw on various sites) napa sells this combo joint, and the part number is #348. I went to napa the other day, get this u-joint, and it doesn't seem to fit either the driveshaft or the axle. Anyone have any ideas? did I get the part number wrong or something?