1971 198 slant six Carb

The C6018 that Autozone shows is the correct carburetor. It's the same as you have. It's just not available anywhere. I think if you want that particular carburetor, your only choice is to rebuild it or have it rebuilt.

The Autoline C6018 is available at Rockauto for $209.79 (less the core of $65.00 for your old carb, the C6018 is only $144.79)
RockAuto