Generally, small blocks had the smaller u-joint size while big blocks had the bigger size. Things get more confusing with 351C-4Vs. Automatics had small joints and 4-speeds had the big u-joints. You can get a hybrid u-joint or you can make your own hybrid by just swap caps on the opposite ends.
Then there are the differing length yokes. Some car lines had short yokes and some used longer ones. Econolines have long yokes. I know that for a fact since I swapped a 72 Cougar 9" rear end into my 74 Camaro. Overall width was very close and the spring width is within 1/2 inch. I used a longer Econoline yoke and then I didn't even have to touch my driveshaft length!