Your front u-joint is called a ball-and-trunnion. It requires a press (I've only been involved in getting one replaced and that was in 1981). RockAuto doesn't list it. You might try NAPA, but they are getting to be more like the Cheapo auto parts stores all the time.
The Dart I worked on back in 1981 was an original 273 hi-po/904 car. I know some or more 727's had slip yoke in 1965, but I've yet to see a 65 904 with a slip-yoke (but that really is not a lot of cars)
1965 was the year that Chrysler phased out the ball-n-trunion driveshaft in favor of a slip yoke with a cross-n-roller U-joint. For the most part, B-body and C-body 727s were slip yoke in 1965, and A-body 904s were mostly ball-n-trunion. Since it was a transition year, both style transmissions can be found in A, B, and C bodied automatics. Almost the entire lot of 1965 A833's were ball-n-trunion, for A, B, and C body cars. Ball-n-trunions, if serviced, will last forever (make sure the dust boot isn't broken).