There are no stickers on the door or under the hood?
Pull the ashtray out and read the numbers on the bottom, they are stamped in. The long number is the part number (I think), eitherway it changed from year to year. Also there is a couple other numbers like 12 82. My guess is this ashtray is from Dec. 1982. Thats what was inside my 1983. Also I found an ashtray at the junk yard out of a sub. the numbers were like 02 89 or something. I cant remember, but it was close to the year of the sub (one year early). This may be a easy was of identifing the year of the trucks. Anyone else know anything about this ashtray thing? Check you trucks if you have the og ashtray and try to verify this information, I may be onto something with this, or I could be wayyyy off
Its worth a shot!