What u-joint do I need?

all you can do is go back, you should have a good idea of what the right one ;looks like now. Its not uncommon look at what your search found several so hang in there its just as confusing to the guys behind the counter too. I have been dealing with this kind of stuff for 40 years it goes with the territory when doing your own work, this happens at shops too, people sometimes do not realize how seemingly something so basic as a U joint can screw up your day, but it can. good luck.