not sure what is different besides the part numbers

from the (Nov. '71) 1972 Parts Catalog & (Sept. '72) 1973 Parts Catalog:
BARRACUDA & CHALLENGER

23-67-76
3431 518 = CRANK w/PIN, Wiper Drive Variable Speed
3431 553 = CRANK w/PIN, Wiper Drive 2 Speed (same as '72/'73 B-body)

23-67-79
2822 291 = LINK, Wiper Pivot Connecting

2822 292 = LINK, Wiper Drive 2 Speed
3431 514 = LINK, Wiper Drive Variable Speed