That particular Ballard is a mongrel. But I did own a number 2 in 32 Long that was made with DST. Some idiot ground a notch in the side of the action so they could take the firing pin screw out. I didnt  know about Peter Nagle then.

I've owned and own still a No. 2 with DST and they sometimes are reversible firing pins, and sometimes centerfire only. Of course if there was no rimfire equivalent of the chambering they were always CF only. And in the case of the #3 they have never had a firing pin retaining screw at all and breech blocks need to be split to replace a firing pin. They're also 99.9% .22RF, but I know a guy who has one rare factory chambered in .22WCF, but don't recall if his breech block was like a #3 or like typical CF breech blocks. 
I've seen a few #3 Ballard rifles with DST, but honestly don't recall if they had a firing pin screw, or were like typical #3 single trigger blocks.
It's always puzzled me why Marlin made the #2 firing pin screw so low that it wont come out usually without dropping the breech block. I have had a couple #2's that the screw just cleared the receiver and came out without dropping the block.