I sense a little confusion, or it might just be the way I read it.
A VOR indicator, also know as an OBI (Omni Bearing Indicator) has only the one vertical needle, obviously driven by the Nav side of your nav/com radio.
The Glide Slope indicator looks very similar for a reason. It is still a VOR indicator, having the same vertical needle still driven by the Nav radio. You could use the G/S indicator as a VOR indicator whether you have a G/S receiver or not!
Adding the G/S receiver enables the glide path (horizontal) needle, which is driven by the G/S receiver ..... not the Nav radio. It also provides the course needle information (transmitted by the ILS system) to the Nav radio which drives the indicator the same as it would if receiving a VOR signal.
In essence, The G/S indicator is really two seperate indicators (built into one housing), driven by two seperate receivers.
You can't run separate VOR and G/S indicators off the same Nav radio (there's no good reason to even try), nor can you have two separate Nav receivers driving the same VOR or G/S indicator. For true redundancy, each indicator needs it's own separate receiver. I assume you don't yet have a G/S indicator, so you still need that anyway to use the Narco's G/S capability. If you buy the Narco (and G/S indicator), that leaves your King system intact to do with as you please. The whole idea of having dual nav/com capability (with or without G/S) is redundancy, especially for IFR/IMC flight. Only a complete electrical failure followed by a dead battery should incapacitate both systems.
The 152 I'm working on has 2 MX-300 nav/coms. The first drives the course needle of the G/S indicator in the top hole in the panel. The second MX-300 drives the VOR indicator in the second hole. A seperate G/S receiver mounted behind the baggage area provides the glide path signal directly to the G/S indicator. All 3 radios receive through the original Nav antenna mounted high on the vertical stabilizer, by using a triplexer (3-way antenna splitter).
I've tried to simplify the operation, but may have inadvertantly confused you in the process.
