@sk0941 +FMS/Garmin-y retrofits. But true classics will keep flying one way or another, and in MSFS, its quite easier if one wants to go old school. Already can fly US like it's 1958 with all the original VORs, NDBs, etc from that era. You can also go all celnav (celestial navigation) and fly your DC-6 or Connie that way, which is how they did it before gyroscope INS systems became a thing.
https://flightsim.to/file/71888/golden-age-of-air-travel-u-s-navaids-as-of-1958
https://flightsim.to/file/17738/celnav-for-msfs-celestial-navigation-sextant
The Wing42 B247 included old AN type radio beacons globally for navigation (where they existed at the time, which was limited coverage). The mods and community stuff will expand with time.