So I bought my 1968 V35A Bonanza in April of 1979. It had the latest state of the art equipment, including a DME, dual KX160 Nav Com, a KR80 ADF, and a Brittain pneumatic autopilot. Here is what it looked like at the time.
After I moved from San Jose, CA to Charlotte, NC the avionics were upgraded with KNS80, KMA20, KY92, KX170B, KR85 ADF, followed by adding a KCS55A. I could navigate direct to any point in the NAS using the KNS80. I still have the ASI and the KNS80 in my panel In 1980 we added the WX-7A Stormscope and replace the Brittain autopilot with the Stec 60-1.
By 1990, I replaced the Wilcox transponder with a KT76A with mode C, upgraded the Stec 60-1 to a 60-2, replaced the Ryan Stormscope with a WX-1000+, added a KLN88 Loran, an RCA electric AI, and an Argus 5000 moving map. The KY92 was replaced by a KY197A Com and the Alcor single probe EGT was replaced with a 6 probe JPI unit. In 1994 the KX170 was replaced with a KX155. Here is a picture from 1990.
I added a Shadin Miniflo in 1996, and in 1998 upgraded the Loran to a KLN90B that was approved for GPS approach. The Argus 5000 was replaced by a color unit, the 5000CE.
In 2000, the KMA20, KR87, KX155, and KLN90B were replaced with a GMA340, GNS430, and an AICD II AM/FM radio/CD player for in flight entertainment. As an avionics shop owner, I got 40% to 60% off on Garmin equipment, and I added an Stec Yaw Damper and GPSS. The GPSS unit cost me $600. In 2001 I sold the company, but before I did, I replaced the GNS430 with the new GNS530 and sold the GNS430 for more than I paid for the GNS530. In 2005 I replaced the transponder with the GTX330 which provided Mode S TIS for traffic and the GDL69A for XM weather and entertainment, so the AICD was removed.
In 2007, I had the GNS530 upgraded to GNS530W. In 2013, I added the Garmin GDL88 ADS-B In/Out system so that added traffic and free weather in the cockpit, but I kept the GDL69A because its weather products are superior. In 2015 I added the FS210 as I was then working for ForeFlight and with the team that added support for the Garmin panel flight plan transfer and weather/traffic data. Because it was company related, it did not cost me anything.
In 2018, I replaced the GNS530W with the GTN750 and added the 7 inch PFD version of the G500TXi and the G5 Battery version as the backup. Much of the older stuff came out at the same time including the audio panel which was replaced by the Garmin remote GMS35 and the push to command audio function to operate the GTN and audio panel came along with that upgrade. I also added the B&C backup alternator.
QuoteBy 2022, I had realized that the 7 inch PFD was a mistake and updated it to the dual screen PFD/MFD version. I also replaced the GTN750 with the GTN750Xi and sold the old unit for $3,500 more than I paid for the Xi. I also had the WX1000+ Stormscope removed and replaced with the WX500 so it would interface with my GTN and G500TXi. My next move is to get the latest version of software on the GTX and G500 systems.
I put the GFC500 mode control panel at the top of the stack, since I really like that position just under the glare shield (makes it feel like a “big plane” to me :) ). iPad on the right is much preferable to me than on the yoke where it moves around and requires looking down then back up in IMC. I can also mount it on the left side, which I do if flying a in hard-IMC since it keeps it in view a bit better.
GNC-300XL is old, but the radio still works great and it pushes a bearing pointer to the G5. Old secondary NAV receiver works just fine and has an ILS receiver too, for a completely separate backup to the digital systems.
@NCYankee impressive your trusty KNS80, I flew many years behind a KNS80 and a Garmin GPS150. The Garmin 150 was not IFR, but I believe it was RNP5 compliant, which the KNS80 wasn’t. In any event many ILS-es into foggy Linate using the KNS80.
I am making the retrograde step of replacing my twenty year old KI-825 with an analogue KI-525A. The KI-825 is uneconomic to repair, and a G5 doesn’t speak to the KFC200, which the KI-525A does. The avionics shop health checked the rest of the slaved HSI system, before deciding to replace the unit. There seems to be a plentiful, possibly inexhaustible, number of serviceable KI-525A units. A GI-275 would have required more surgery in the form of WAAS GPS (my 530/430 combo is old skool). I may swap my 530 for a 530W but not sure it is worth it. I will in due course upgrade the GTX330 to a GTX335, making the Bonanza ADSB-Out compliant.
A full surgical upgrade (Glass, Digital A/P) in Europe seems a big, possibly uneconomic, investment
It is mostly as it came from the factory in 2002. The Mode C TXP was soon changed to the GTX330. For the LH SN3500 EHSI I got a Field Approval done by a US pilot who turned out to be a senior FSDO inpector and did an amazing job for free 
Then the EDM700 was changed from the 2" to the 3" version (JPI did it for $300) and moved from the far right to the left panel which is much better. Later the RH SN3500 was installed, together with the SG102 AHRS.
I would install 2×IFD540 as photoshopped here
but cannot find an installer in the UK who would likely do a decent job while being flexible on the functionality; the 1 or 2 good ones hold the view that any wire not shown on an STC is illegal. Currently, the KLN94 is fine for everything in European IFR except LPV.
That’s a Robin back from the future
2013..note the French sticker KLN90 not approved for approach :-), it was removed when going N reg …..
2024
I like the AV20S just for the TAS, OAT and Voltage indications in the same field
On my next wishlist GI275 and new panel overlay….removing redundant instruments.
C41AP hopefully continues to work, its fantastic in LNAV GNSS roll steering (engaged by just pushing the HDG knob) in combi with SN and GNX. Although it would do some good on the CG when going for GFC500. Not so much on my wallet.
The ADL190 is interfaced with the GNX for Flight Plan Transfer and provides weather on my pad and on the GNX FIS-B page.
I dumped the Shadin miniflow for a FS450, cheap solution as I got to replace the fuel flow sender (floscan) at the same time which was worn out.
