I don't know how you came up with more than 2 listings for any particular model, unless it has something to do with using a phone. Now, by doing a search on VTI's site for the p/n UB:400021, comes up with 4 listings. The two that both say no safety have the same p/n except one has a capital N:
UB:400021/noSafety
UB:400021/NoSafety
The first one with the small n is the one that says round head. I don't have my guns with me to check but I think they are all round head? Both my Cimarrons and my Colts. I don't know what other style they would carry for a SAA. Personally, I think those two p/n's are the same part with slightly different descriptions.
And by the same token, I think the other two p/n's with safety are also the same part with two different p/n's:
UB:400021/w
UB:400021/wSafety
You could call them and ask to be sure. And if you do order from them, to take advantage of combining shipping, order one of their reduced power mainsprings as well. Your gun will feel much better! Two of my 4 Colts have had action jobs and none of my Ubertis (Cimarrons) have, but every one has a lighter mainspring in it!