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The original GM part number is 14056557 replaced by 15598419. The module was used on 1979 - 1982 C/K 1/2, 3/4 & 1-ton trucks with pulse wipers. OEM is obsolete. Except by sheer chance, you're unlikely to find any reproductions. Rarely, they pop up on E-bay either as take-offs or NOS. Best bet is probably to scour the yards for a doner. Because of the vintage, chances are high that any electrolytic capacitors on the board will have dried out and need to be replaced.
Grizzly, 14056557* is the OEM number for the module, which is NLA. The OEM number for the switch is 14028808*, also NLA. Both numbers are directly from the GM 52A parts manual (asterisks color keyed to image).