Rebuilt my brakes and mines an 72 with early discs, used the early ones from GSF they eorked fine for me.
From what i can remember what i found out about early/ late calipers.
Early calipers aperture (where the pads go in) is 47mm wide and has 2 bleed nipples. Lates are about 55mm wide.
Early pads are 15mm thick retaining clips held in with spring type pins, Lates are 19 mm thick and have bigger retaining springs and have circlip type pins.
Early discs are 8mm thick and Lates are 13mm thick.
Thay are handed due to the cut out on the pistons, cut outs go to wards the bottom.
Early brake bits are expensive and Lates are cheeper.
Prehaps we can make this a sticky so that people can keep adding to it and get a definitive answer to the 71/72 brake saga.