Not always. The '70 Road Runner probably has the 2 5/8" (7290) u-joints and the '67 A-body should have the 2 1/8" (7260) u-joint. They do make a conversion joint for that application if that's what you have. If one of the 3rd members has an oddball pinion flange (such as an Imperial or Chrysler w/ CV joints, or an early u-bolt type) you'll probably not find a conversion joint for that. Changing pinion flanges is an option if you have a spare of the correct u-joint type for that particular pinion gear.
