My washer didn’t come with a fabric softener dispenser but I want to put one on it. I was told that part #63580 is what I need but it seems too simple. Is that the only thing I need to make it work? does it just fit over the existing agitator or do I have to change out the agitator as well?
My agitator had stopped spinning so I ordered the agitator repair kit. Very easy to replace, btw. But, while looking for the part, I noticed that you could purchase a fabric softener dispenser and it was very inexpensive and I ordered that as well. All I did was instead of replacing the cap on the agitator, I just snapped the fabric softener in place of it. Of course I searched for parts by model #. Everything is working! So, to answer the original question…no, you do not have to purchase the whole agitator. You can can just remove the cap on the agitator and place the fabric softener in place of it. 
Well good, thanks for that update. Just go very easy on the fabric softener, you’d be amazed at how that stuff can gum up the works.