Well, the radio set that Scott Thomas came up with for the Beech 18 doesn't have a Nav 2. What it does have instead is a standby channel for Nav 1. There's a button on it to switch them back and forth. Otherwise, it works the same as the default DC-3 radio set. It's one of my preferred radio setups in FS and has found it's way into a lot of aircraft. I'm kind of fond of the setup in the Spartan as well.
Just noticed that one of the frequency adjusters on it says Nav 2. But if you look at the tool tip, it doesn't show it as Nav 2, but as a standby for Nav 1.