Was the system still sealed or left open? At a minimum, you should replace the dryer. Not sure on the oil requirement, but you need to remove the existing R12 oil as it isn't compatible with the oil for R134.

You might want to pull the evaporator and clean it. The one on my 83 was completely clogged with leaves and dirt. That gives you access to the expansion valve as well, which I would consider replacing as well.

Bob Garrett
83 Toy Pickup
95 FZJ80
Shawnee, KS