When we restored PA474 to airworthiness at Waddington in '65-'68 one of the jobs I did was installing an inverter system to provide 115v 400 Hz power for a TACAN installation fitted by the "Fairies". So, as originally returned to flight, she was navigated using the tried and tested paper and pencil methods, baked up by range and bearing fixes on the then standard standard military TACAN beacons. It was still there the last time I had a chance to climb aboard in 1977 during an overnight at Northolt, but I guess she'd have a Garmin these days...