Inside might be a different story, but I think you should be able to readily use most of the exterior placards for a NA 58 with the possible exception of the door operating instructions. I suggest you check the parts manual for specific wording to compare to what you find for the NA 58. Many paint shops fabricate their own from transfer kits, so check that possible source also.
If you don't have a parts manual for the P Baron I can send you a copy of the applicable pages that display the placards. Just contact me off list.