Take your old ones out first. Take the old ones to the store you by them from and have them put a micrometer on both end caps to get an EXACT measurement of them. I did U joints on a friends 92 Wrangler, and it took 3 stores before we got the correct ones. The tape measure the first guy used, they looked the same, but wouldn't go back in. I mic'd them and they were 1/16" off. At the 3rd store the guy mid'd them there and they were right on. Went to my shop, fell right in the hole perfectly. I've done Dakota U joints, Chevy pickup U joints, every single time I made multiple part runs. When I had my new d/s made for Hack Job, the shop put new U joints and a yoke on it too, so that's the only time I've never had a problem because it was all done by a specialty shop.