Master cylinder questions (original versus replacement parts)

[nge]

I am replacing my the original master cylinder in my 1973 Charger. The car came with front disk brakes and drum brakes in the rear.
My problem is  that I have bought 3 replacements one form Cardone, One from NAPA and one from Raybestos.
each have three (3) holes in the floor of the front and back reservoirs.  The 3 new replacements only have 2 holes. (still one brake line connection in the front half and one for the back half, the extra holes are internal_
The old one has the rounded (half circle) reservoir in the front.  The 3 new ones have a square front reservoir with rounded side on the back of the rear reservoir.
Does anyone know what difference between 2 or 3 ports signifies?
Is this just the way it is in the replacement part world?

[ht4spd307]

do you still have the original if so bite the bullet and get the original one stainless steel sleeved and you'll never need another all the rest is Chinese crap

[Mopar Nut]

do you still have the original if so bite the bullet and get the original one stainless steel sleeved and you'll never need another all the rest is Chinese crap