The avionics package is somewhat different in each of the Lear 35's.
Most of the 35's have the standard stuff I would think: FD, HSI, Dual VOR/LOC, DME and ADF.
All the 35's I have flown have a GPS, mostly Trimble, but some Garmin and the KNS90. Off course most of these units have been located a little different in each airplane.

These are off course all cargo airplanes. I would dare to say MOST corporate 35's would have FMS, TCAS and GPWS.

I have flown a 35 with a navigation system were you make adjustment for Magnetic variation. Need for navigation close to the North/South pole.

Some 35's have a retro fitted higher take off/landing weight kit. With it comes a Vmo/Mmo select button. It limits you speed at certain weights.

I'm sure there are more that I can't think of at the moment.

The Lear I have flown have been spread over somewhat a wide range of serial numbers so that makes it more fun. Differences in the electrical system, cabin system, Alcohol anti-ice system, emergency battery system.
And off course they may or may not have been retro fitted with a kit that fixes some of the earlier serial number design features.

It's kind of amazing that the FAA allows you with a LR-JET type rating to fly the 20, 30 series and the Lear 55.
I have some experience with the 24's and while it had many similarities with the 35's it was also very different. It too off course had different models.
For example the 35's will disengage the starter for you (hopefully) but in the 24's you had to do that. Some of the 24's had a electrical wing and stab anti-ice system while 35's use bleed air.

It's the only Jet I have flown so far. I think at some point in my life I will look back on my time in the Lear with a massive amount of Nostalgia.