Lowell passed away earlier this year, but I understand that his family is carrying on the business of making replica bikes. The Kennedy family isn't on the web as far as I know, so you'll have to write. You buy a highwheel by the size of the wheel. If you are buying new from one of the folks above, they'll help you determine the wheel size you need. You want to buy a highwheel that looks as much like an original as possible.
Good replicas keep that small clearance.
Bad replicas have two or more inches. Originals were trying to keep the cycle as compact as possible, and also make it easier to get into the saddle. Poor replicas use a single sized tube the whole length. A spoon brake with a lever that follows the curve of the handlebar. Shame on you.