What the "original" carb rebuilders did was to clean up the carb bore to oversize and put a brass sleeve on the slide. In other words the bore is left oversized.
An epoxy product might be a option for application to the slide. I am wondering how well an epoxy product will adhere to the the pot metal especially as the slide needs to get shaved down to size. It might take a trial and error session to see how well that works out and then let it soak in the new ethanol blended gasoline.