I think Ron wanted to verify his hopes that it was a Custom Cab by finding that evidence on the data plate. I don't think the data plate will tell you if you have a Custom Cab or not. His glove box door must not have had the tag on it, or was gone, because he said ''There is no ID plate on the door post"., which is not where they are found. So I listed the clues to help him figure out if he had a Custom Cab. The chassis / title vin code will tell him some of the info to put on the new tag, and as you said, there is almost always some original paint under the dash, or somewhere to tell what the paint code would be. The speedometer gears in the trans (if he has the original trans ) will tell what the differential ratio was.