You got me on this one..... the best price I can find on this GM part number is $83... so I will discount it to $50 you pay shipping.

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GM 88894341 Water Pump SBC Pump - Late-style cast iron water pump with long mounting legs. This pump has a reinforced snout and 3/4" diameter shaft. The end of the shaft is reduced to 5/8" diameter. Used on the 350 HO 330 HP, 383 GMPP crate engines, and ZZ4. [Old P/N 12529305] -- 83.23
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jc