I have converted quite a few cars to 134 and all I have done is changed the fittings and evacuate then charge with 134.
All the hype about changing O-rings and special hoses and receiver/drier replacement is not necessary.
Some of the newer kits come with improved oil in the can so it is added during the recharge.
Just my after 30 years in the dealership
Gus

64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60