I blasted the inside with fresh glass beads and it seems like I should have used some more powdery media to get into the bottom of the pits. You might be able to remove most of the inside pitting with an agressive scotchbrite pad on a die grinder. None of the pitting penetrates completely through the metal. Drain plug is missing the gasket.
The item "BUICK NAILHEAD 364 401 425 REAR SUMP OIL PAN 57 58 59 60 61 62 63 64 65 66 GS" is in sale since Monday, October 14, 2019. This item is in the category "eBay Motors\Parts & Accessories\Vintage Car & Truck Parts\Engines & Components\Oil Pans". The seller is "jhoppeolds" and is located in Milwaukee, Wisconsin. This item can be shipped worldwide.