Thanks.
The front retractor belts:

F-480
3861200
4773

F-481
3861201
4773

The rear retractor belt has:
9801
3760183
4372
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I'm guessing the last #'s from each set are the date codes - '73 & '72 respectively. Perhaps the rears were carry-overs from the previous year while the fronts were a new style for late '73 or early '74 model year?