Early A dual master recommendation?

Hi all,
as my 63 Dart seems to need a brake overhaul, decided to upgrade the master cylinder too. The subject probably been beaten to death already but I can't seem to find a definite answer which one to choose, so somebody please chime in.
As my car is and will be registered as a "classic vehicle", here in Spain they are kinda strict about any upgrades, regardless their necessity. So I will have to stick with the original 9" drum brakes, non power assisted. I would like to have the new master appear as close to stock as possible, with minimal modifications needed and hope nobody will notice. Have a single cylinder in now, not original but looks like one.
So I need a 1967 master cyl then? Or are the 68, 69, 70 and so on identical? I remember reading in some thread that a 1971 and up would be somewhat better, is that so?Looking at ebay ads, they all look the same but perhaps in reality they're not?