An original 40-50s carbs is pot metal (zinc) that has be plated. Once the plating is gone its gone and you are left with a gray zinc surface.
The throttle body is usually cast and can be blasted/plated but be careful that the vacuum passages are still open.
Getting them re-plated is an option, or polishing them and then clear coating might be acceptable... but the original plating process is pretty much impossible to get due to the toxic chemicals required.
