Which aluminum master cyl for 71 Duster

The part number that 340doc posted is a two bolt plastic reservoir master cylinder. Originally for mid 90's Dakota, with I believe a 24mm bore. There are at least 6, maybe as many as 10 master cylinders that look the same, just with different bore diameters, thread sizes, and some don't have any provision for a manual pushrod. As in, no groove for the rubber ring that retains the pedal pushrod.