Good point in a leaking float. His over flow problem could just be a float set too high or the float valve leaking. Those float valves has a very small rubber seal on them that you can barely see. If its been a few years since this carburetor has been rebuilt, there is a good chance it's been destroyed by ethanol.

The good news is a rebuild kit is dirt cheap at Autozone. I use a 1971 Ford F100 rebuild kit for my 2100 and it costs less than $15. It only takes 20 or so minutes to rebuild the carb as well.

There are plenty of YouTube videos out there on how to rebuild one.

There are only a few basic tools needed to rebuild a 2100. Most people use nothin more than a can of beer, a screw driver, and an adjustable wrench. I don't drink alcohol, so I substitute a diet Cheerwine for the beer.

When I can't have a diet Cheerwine I substitute it with diet Dr Pepper Cherry.