No one in this thread has shown the correct pads for OP's brakes,
early 1970s Weinmann center pull. That should be 4-dot, "salmon", in a 3-sided aluminum (not steel!) holder. Even the 3-sided holder came in two variants, one with little pokies to try to keep the pad from slipping out the open end, but that style is too new for OP's bike, he needs the one without the pokies. That's the one on the left in this pic:
I can supply a set of four of each of those types.
Oldest vintage, well-used, set of four, $50:
Sorry about the high priice but it's my last set.
Mid-vintage ('pokies'), well-used, set of four, $20:
Newest vintage, 4-sided holder with 'windows', well-used, $10:
Newest vintage, 4-sided holder with 'windows', NOS, $30:
That's for the 4 pads with holders, not the display card, which I am keeping.
if you want I can also mount four Kool Stop salmon Weinmann-repo rubbers in any of the holders shown above, but I charge full retail* on the pads and $20 labor, maybe worth it to you if you don't have a vise or other way to install them. Installing them in the 4-sided holders requires bending one of the sides down, and it'll break off, leaving it as a 3-sided holder. So you will forever after be required to put them in the bike facing the right way, so as not to die.
*Porkchop BMX sells them for $38/set, the only place I looked, tell me if they're cheaper elsewhere.