Twister, gold, or just duster

Can these models be told apart from the VIN (2nd digit L,M,H,P) or is this a data plate option code thing only? If so, how or what is the coding on any or either case? Problem: Looking at a 30+ year old car, that is now devoid of decals and most OEM paint, how can you tell what it is or what supposed to be there originally? (A bodies are a new thing to learn for me, I'm normally a B body guy.)