galled left rear axle spindle. repair? replace? buy used or aftermarket?

[alchemy]

Buy a new axle from one of the trusted sources listed above for a 39-41 Ford. Easy peasy. The hard part is properly shimming the housing on reassembly. The gaskets aren’t just gaskets. They are shims and if you measure them accurately upon removal, you should be able to use new ones of the exact size and get proper fit on assembly.