@Peter the plan would be to install a G5 EHSI which, if I understand from your experience with your Sandel unit, does auto slew when the next leg activates on the KLN94, although without the capability for roll steering.
I spend a fair amount of time in aircraft with roll steering (G1000/GFC700) and must confess I haven’t noticed the subtlety…compared to say heavy iron FMS.
The GI275 needs a WAAS GPS apparently.
You can use a glareshield antenna to satisfy the WAAS requirement for the ADHARS and KLNs output for navigation.
Now the first avionics shop says that the KLN94 is not covered by the AML STC from Garmin, which seems odd to say the least. Given the population of KLN94s it would be odd that Garmin didn’t include it.
That is the position that only stuff in the IM can be connected…
If the KLN outputs the same guidance information as the KX there is no reason why it shouldn’t work (as the KX is in the install manual).
What it most probably won’t do properly is feed the moving map overlay.
You could go the easy way and get a G 175 :-)
Why would it not move the map? If the G5 is compatible with the standard “aviation data stream” (which everything from the GNS430 on emulates) that will drive a moving map fine.
This would be dead easy to test on the bench, but I would be surprised if anybody is going to put in the effort. Well, I have a spare KLN94 so if somebody can loan a G5, we can wire it up.
Move the map yes (the map moves on its own from G5 or GI275 own gps input).
Draw hold patterns, i don’t know as GPS-Aviation via RS232 carries less data than Arinc or MapMX.
Only question is if either G unit supports GPS aviation as the navigators it is supposed to interface with all provide either Arinc or MapMX. So from Garmin’s perspective there’d be no incentive to support a third format.
Thank you for the input. Spoke with second avionics shop who were very helpful, but interestingly @T28 suggestion of swapping a to a GPS175 comes up.
The KLN94 will speak to an Aspen, but not a G5. However, apparently the KLN94 is not approved for IFR approaches under CAA/EASA, even though it is under FAA. EASA in its wisdom only approved it for IFR BRNAV with a CDI and NAV source annunciator. The Flight Manual Supplement that was approved was only BRNAV.
Am now getting a quote for hooking up the KLN94 to a KI209A, but may conclude that it is a VFR box.
apparently the KLN94 is not approved for IFR approaches under CAA/EASA
That is outrageous, especially since those installations pre-date the EASA takeover of the universe 
But, yeah, if you have to use a shop to install it, you have to go with whatever they say.
For the ignorant…. what is roll steering (and how else does an AP steer a heading?)
