Best way to connect two different size/height rain barrels

I want to connect these two rain barrels that were gifted to me. Thoughts on the best way to do this seeing how the connections at the top are two different sizes? The connections at the bottom are the same sizes but different heights and purposes. The smaller barrel doesn’t have an official bottom connection, just its spigot. The larger barrel has a bottom connection and spigot, the bottom connection is lower than the spigot on the smaller barrel and the higher connection (where you are supposed to install its spigot) is higher than the spigot on the smaller barrel.

I haven’t installed the downspout diverter yet, so I can have the gutter go into either barrel at this point.